WorldWideScience

Sample records for surprisingly optical electron

  1. Electron optics

    CERN Document Server

    Grivet, Pierre; Bertein, F; Castaing, R; Gauzit, M; Septier, Albert L

    1972-01-01

    Electron Optics, Second English Edition, Part I: Optics is a 10-chapter book that begins by elucidating the fundamental features and basic techniques of electron optics, as well as the distribution of potential and field in electrostatic lenses. This book then explains the field distribution in magnetic lenses; the optical properties of electrostatic and magnetic lenses; and the similarities and differences between glass optics and electron optics. Subsequent chapters focus on lens defects; some electrostatic lenses and triode guns; and magnetic lens models. The strong focusing lenses and pris

  2. A surprise in the first Born approximation for electron scattering

    International Nuclear Information System (INIS)

    Treacy, M.M.J.; Van Dyck, D.

    2012-01-01

    A standard textbook derivation for the scattering of electrons by a weak potential under the first Born approximation suggests that the far-field scattered wave should be in phase with the incident wave. However, it is well known that waves scattered from a weak phase object should be phase-shifted by π/2 relative to the incident wave. A disturbing consequence of this missing phase is that, according to the Optical Theorem, the total scattering cross section would be zero in the first Born approximation. We resolve this mystery pedagogically by showing that the first Born approximation fails to conserve electrons even to first order. Modifying the derivation to conserve electrons introduces the correct phase without changing the scattering amplitude. We also show that the far-field expansion for the scattered waves used in many texts is inappropriate for computing an exit wave from a sample, and that the near-field expansion also give the appropriately phase-shifted result. -- Highlights: ► The first Born approximation is usually invoked as the theoretical physical basis for kinematical electron scattering theory. ► Although it predicts the correct scattering amplitude, it predicts the wrong phase; the scattered wave is missing a prefactor of i. ► We show that this arises because the standard textbook version of the first Born approximation does not conserve electrons. ► We show how this can be fixed.

  3. Optical electronics

    CERN Document Server

    Yariv, Amnon

    1991-01-01

    This classic text introduces engineering students to the first principles of major phenomena and devices of optoelectronics and optical communication technology. Yariv's "first principles" approach employs real-life examples and extensive problems. The text includes separate chapters on quantum well and semiconductor lasers, as well as phase conjugation and its applications. Optical fiber amplification, signal and noise considerations in optical fiber systems, laser arrays and distributed feedback lasers all are covered extensively in major sections within chapters.

  4. No surprise in the first Born approximation for electron scattering

    International Nuclear Information System (INIS)

    Lentzen, M.

    2014-01-01

    In a recent article it is argued that the far-field expansion of electron scattering, a pillar of electron diffraction theory, is wrong (Treacy and Van Dyck, 2012 [1]). It is further argued that in the first Born approximation of electron scattering the intensity of the electron wave is not conserved to first order in the scattering potential. Thus a “mystery of the missing phase” is investigated, and the supposed flaw in scattering theory is seeked to be resolved by postulating a standing spherical electron wave (Treacy and Van Dyck, 2012 [1]). In this work we show, however, that these theses are wrong. A review of the essential parts of scattering theory with careful checks of the underlying assumptions and limitations for high-energy electron scattering yields: (1) the traditional form of the far-field expansion, comprising a propagating spherical wave, is correct; (2) there is no room for a missing phase; (3) in the first Born approximation the intensity of the scattered wave is conserved to first order in the scattering potential. The various features of high-energy electron scattering are illustrated by wave-mechanical calculations for an explicit target model, a Gaussian phase object, and for a Si atom, considering the geometric conditions in high-resolution transmission electron microscopy. - Highlights: Treacy and Van Dyck (2012) argue that the far-field expansion of electron scattering is wrong. The chief theses of that former work are wrong. There is no room for the missing phase proposed by Treacy and Van Dyck. There is no violation of the intensity conservation to first order in the scattering potential. Calculations for a phase object and an atomic target confirm traditional scattering theory

  5. Electron impact ionization of heavy ions: some surprises

    International Nuclear Information System (INIS)

    Younger, S.M.

    1986-01-01

    This paper reports the results of calculations of electron impact ionization cross sections for a variety of heavy ions using a distorted wave Born-exchange approximation. The target is described by a Hartree-Fock wavefunction. The scattering matrix element is represented by a triple partial wave expansion over incident, scattered, and ejected (originally bound) continuum states. These partial waves are computed in the potentials associated with the initial target (incident and scattered waves) and the residual ion (ejected waves). A Gauss integration was performed over the distribution of energy between the two final state continuum electrons. For ionization of closed d- and f-subshells, the ejected f-waves were computed in frozen-core term-dependent Hartree-Fock potentials, which include the strong repulsive contribution in singlet terms which arises from the interaction of an excited orbital with an almost closed shell. Ground state correlation was included in some calculations of ionization of d 10 subshells

  6. Bimolecular Excited-State Electron Transfer with Surprisingly Long-Lived Radical Ions

    KAUST Repository

    Alsam, Amani Abdu

    2015-09-02

    We explored the excited-state interactions of bimolecular, non-covalent systems consisting of cationic poly[(9,9-di(3,3’-N,N’-trimethyl-ammonium) propyl fluorenyl-2,7-diyl)-alt-co-(9,9-dioctyl-fluorenyl-2,7-diyl)] diiodide salt (PFN) and 1,4-dicyanobenzene (DCB) using steady-state and time-resolved techniques, including femto- and nanosecond transient absorption and femtosecond infrared spectroscopies with broadband capabilities. The experimental results demonstrated that photo-induced electron transfer from PFN to DCB occurs on the picosecond time scale, leading to the formation of PFN+• and DCB-• radical ions. Interestingly, real-time observations of the vibrational marker modes on the acceptor side provided direct evidence and insight into the electron transfer process indirectly inferred from UV-Vis experiments. The band narrowing on the picosecond time scale observed on the antisymmetric C-N stretching vibration of the DCB radical anion provides clear experimental evidence that a substantial part of the excess energy is channeled into vibrational modes of the electron transfer product and that the geminate ion pairs dissociate. More importantly, our nanosecond time-resolved data indicate that the charge-separated state is very long lived ( 30 ns) due to the dissociation of the contact radical ion pair into free ions. Finally, the fast electron transfer and slow charge recombination anticipate the current donor−acceptor system with potential applications in organic solar cells.

  7. Bimolecular Excited-State Electron Transfer with Surprisingly Long-Lived Radical Ions

    KAUST Repository

    Alsam, Amani Abdu; Aly, Shawkat Mohammede; Usman, Anwar; Parida, Manas R.; Del Gobbo, Silvano; Alarousu, Erkki; Mohammed, Omar F.

    2015-01-01

    We explored the excited-state interactions of bimolecular, non-covalent systems consisting of cationic poly[(9,9-di(3,3’-N,N’-trimethyl-ammonium) propyl fluorenyl-2,7-diyl)-alt-co-(9,9-dioctyl-fluorenyl-2,7-diyl)] diiodide salt (PFN) and 1,4-dicyanobenzene (DCB) using steady-state and time-resolved techniques, including femto- and nanosecond transient absorption and femtosecond infrared spectroscopies with broadband capabilities. The experimental results demonstrated that photo-induced electron transfer from PFN to DCB occurs on the picosecond time scale, leading to the formation of PFN+• and DCB-• radical ions. Interestingly, real-time observations of the vibrational marker modes on the acceptor side provided direct evidence and insight into the electron transfer process indirectly inferred from UV-Vis experiments. The band narrowing on the picosecond time scale observed on the antisymmetric C-N stretching vibration of the DCB radical anion provides clear experimental evidence that a substantial part of the excess energy is channeled into vibrational modes of the electron transfer product and that the geminate ion pairs dissociate. More importantly, our nanosecond time-resolved data indicate that the charge-separated state is very long lived ( 30 ns) due to the dissociation of the contact radical ion pair into free ions. Finally, the fast electron transfer and slow charge recombination anticipate the current donor−acceptor system with potential applications in organic solar cells.

  8. Ontological Surprises

    DEFF Research Database (Denmark)

    Leahu, Lucian

    2016-01-01

    a hybrid approach where machine learning algorithms are used to identify objects as well as connections between them; finally, it argues for remaining open to ontological surprises in machine learning as they may enable the crafting of different relations with and through technologies.......This paper investigates how we might rethink design as the technological crafting of human-machine relations in the context of a machine learning technique called neural networks. It analyzes Google’s Inceptionism project, which uses neural networks for image recognition. The surprising output...

  9. Surprise Trips

    DEFF Research Database (Denmark)

    Korn, Matthias; Kawash, Raghid; Andersen, Lisbet Møller

    2010-01-01

    We report on a platform that augments the natural experience of exploration in diverse indoor and outdoor environments. The system builds on the theme of surprises in terms of user expectations and finding points of interest. It utilizes physical icons as representations of users' interests...... and as notification tokens to alert users when they are within proximity of a surprise. To evaluate the concept, we developed mock-ups, a video prototype and conducted a wizard-of-oz user test for a national park in Denmark....

  10. PREVAIL: latest electron optics results

    Science.gov (United States)

    Pfeiffer, Hans C.; Golladay, Steven D.; Gordon, Michael S.; Kendall, Rodney A.; Lieberman, Jon E.; Rockrohr, James D.; Stickel, Werner; Yamaguchi, Takeshi; Okamoto, Kazuya; Umemoto, Takaaki; Shimizu, Hiroyasu; Kojima, Shinichi; Hamashima, Muneki

    2002-07-01

    The PREVAIL electron optics subsystem developed by IBM has been installed at Nikon's facility in Kumagaya, Japan, for integration into the Nikon commercial EPL stepper. The cornerstone of the electron optics design is the Curvilinear Variable Axis Lens (CVAL) technique originally demonstrated with a proof of concept system. This paper presents the latest experimental results obtained with the electron optical subsystem at Nikon's facility. The results include micrographs illustrating proper CVAL operation through the spatial resolution achieved over the entire optical field of view. They also include data on the most critical issue of the EPL exposure approach: subfield stitching. The methodology of distortion correction will be described and both micrographs and metrology data of stitched subfields will be presented. This paper represents a progress report of the IBM/Nikon alliance activity on EPL.

  11. Electron quantum optics as quantum signal processing

    OpenAIRE

    Roussel, B.; Cabart, C.; Fève, G.; Thibierge, E.; Degiovanni, P.

    2016-01-01

    The recent developments of electron quantum optics in quantum Hall edge channels have given us new ways to probe the behavior of electrons in quantum conductors. It has brought new quantities called electronic coherences under the spotlight. In this paper, we explore the relations between electron quantum optics and signal processing through a global review of the various methods for accessing single- and two-electron coherences in electron quantum optics. We interpret electron quantum optics...

  12. Charming surprise

    CERN Multimedia

    Antonella Del Rosso

    2011-01-01

    The CP violation in charm quarks has always been thought to be extremely small. So, looking at particle decays involving matter and antimatter, the LHCb experiment has recently been surprised to observe that things might be different. Theorists are on the case. The study of the physics of the charm quark was not in the initial plans of the LHCb experiment, whose letter “b” stands for “beauty quark”. However, already one year ago, the Collaboration decided to look into a wider spectrum of processes that involve charm quarks among other things. The LHCb trigger allows a lot of these processes to be selected, and, among them, one has recently shown interesting features. Other experiments at b-factories have already performed the same measurement but this is the first time that it has been possible to achieve such high precision, thanks to the huge amount of data provided by the very high luminosity of the LHC. “We have observed the decay modes of the D0, a pa...

  13. Charming surprise

    CERN Multimedia

    Antonella Del Rosso

    2011-01-01

    The CP violation in charm quarks has always been thought to be extremely small. So, looking at particle decays involving matter and antimatter, the LHCb experiment has recently been surprised to observe that things might be different. Theorists are on the case.   The study of the physics of the charm quark was not in the initial plans of the LHCb experiment, whose letter “b” stands for “beauty quark”. However, already one year ago, the Collaboration decided to look into a wider spectrum of processes that involve charm quarks among other things. The LHCb trigger allows a lot of these processes to be selected, and, among them, one has recently shown interesting features. Other experiments at b-factories have already performed the same measurement but this is the first time that it has been possible to achieve such high precision, thanks to the huge amount of data provided by the very high luminosity of the LHC. “We have observed the decay modes of t...

  14. All-Optical Electron Injector

    Science.gov (United States)

    Umstadter, Donald

    2002-04-01

    Conventional electron acceleration at a place like SLAC needs miles to boost particles up to 50 GeV energies by feeding microwaves into a succession of cavities. In recent years we have been developing alternative acceleration concepts, based on lasers focused into plasmas, that might someday do the job in a much smaller space without the use of cavities. Our near term goal is to produce a first stage accelerator that outputs electron beams with lower energy but with properties that are more suitable for x-ray sources, such as those based on Compton scattering or the proposed linear synchrotrons at SLAC and DESY. In the plasma wakefield approach, for example, a terawatt laser beam is focused onto a gas jet, ionizing it and driving plasma waves that move at relativistic speeds. If timed just right, electrons in the plasma can surf the plasma waves to high speeds, as high as 100 MeV in the space of only a millimeter. NanoCoulombs of charge have been accelerated in well-collimated beams (1-degree divergence angle). One problem with this concept is the mismatch between the electron source (sometimes an external photocathode, sometimes an uncontrolled cloud of electrons from the plasma itself) and the incoming laser pulse. We will be reporting methods for generating electrons in a controllable way, namely the use of a pair of crossed laser beams which position, heat, and synchronize the insertion of electrons into the plasma wave. We show that this "all-optical injection" increases the number and energy of energetic electrons as compared with use of only one laser beam. It has been shown theoretically that this approach can ultimately be used to reduce the electron energy spread to a few percent. Besides potential applications to particle physics and x-ray lasers, high gradient acceleration schemes are also expected to benefit the production of medical radioisotopes and the ignition of thermonuclear fusion reactions.

  15. Surprise, Recipes for Surprise, and Social Influence.

    Science.gov (United States)

    Loewenstein, Jeffrey

    2018-02-07

    Surprising people can provide an opening for influencing them. Surprises garner attention, are arousing, are memorable, and can prompt shifts in understanding. Less noted is that, as a result, surprises can serve to persuade others by leading them to shifts in attitudes. Furthermore, because stories, pictures, and music can generate surprises and those can be widely shared, surprise can have broad social influence. People also tend to share surprising items with others, as anyone on social media has discovered. This means that in addition to broadcasting surprising information, surprising items can also spread through networks. The joint result is that surprise not only has individual effects on beliefs and attitudes but also collective effects on the content of culture. Items that generate surprise need not be random or accidental. There are predictable methods or recipes for generating surprise. One such recipe is discussed, the repetition-break plot structure, to explore the psychological and social possibilities of examining surprise. Recipes for surprise offer a useful means for understanding how surprise works and offer prospects for harnessing surprise to a wide array of ends. Copyright © 2017 Cognitive Science Society, Inc.

  16. Electronic tunneling currents at optical frequencies

    Science.gov (United States)

    Faris, S. M.; Fan, B.; Gustafson, T. K.

    1975-01-01

    Rectification characteristics of nonsuperconducting metal-barrier-metal junctions as deduced from electronic tunneling theory have been observed experimentally for optical frequency irradiation of the junction.

  17. Electron quantum optics in ballistic chiral conductors

    Energy Technology Data Exchange (ETDEWEB)

    Bocquillon, Erwann; Freulon, Vincent; Parmentier, Francois D.; Berroir, Jean-Marc; Placais, Bernard; Feve, Gwendal [Laboratoire Pierre Aigrain, Ecole Normale Superieure, CNRS (UMR 8551), Universite Pierre et Marie Curie, Universite Paris Diderot, Paris (France); Wahl, Claire; Rech, Jerome; Jonckheere, Thibaut; Martin, Thierry [Aix Marseille Universite, CNRS, CPT, UMR 7332, Marseille (France); Universite de Toulon, CNRS, CPT, UMR 7332, La Garde (France); Grenier, Charles; Ferraro, Dario; Degiovanni, Pascal [Universite de Lyon, Federation de Physique Andre Marie Ampere, CNRS - Laboratoire de Physique de l' Ecole Normale Superieure de Lyon, Lyon (France)

    2014-01-15

    The edge channels of the quantum Hall effect provide one dimensional chiral and ballistic wires along which electrons can be guided in an optics-like setup. Electronic propagation can then be analyzed using concepts and tools derived from optics. After a brief review of electron optics experiments performed using stationary current sources which continuously emit electrons in the conductor, this paper focuses on triggered sources, which can generate on-demand a single particle state. It first outlines the electron optics formalism and its analogies and differences with photon optics and then turns to the presentation of single electron emitters and their characterization through the measurements of the average electrical current and its correlations. This is followed by a discussion of electron quantum optics experiments in the Hanbury-Brown and Twiss geometry where two-particle interferences occur. Finally, Coulomb interactions effects and their influence on single electron states are considered. (copyright 2013 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Electron quantum optics in ballistic chiral conductors

    International Nuclear Information System (INIS)

    Bocquillon, Erwann; Freulon, Vincent; Parmentier, Francois D.; Berroir, Jean-Marc; Placais, Bernard; Feve, Gwendal; Wahl, Claire; Rech, Jerome; Jonckheere, Thibaut; Martin, Thierry; Grenier, Charles; Ferraro, Dario; Degiovanni, Pascal

    2014-01-01

    The edge channels of the quantum Hall effect provide one dimensional chiral and ballistic wires along which electrons can be guided in an optics-like setup. Electronic propagation can then be analyzed using concepts and tools derived from optics. After a brief review of electron optics experiments performed using stationary current sources which continuously emit electrons in the conductor, this paper focuses on triggered sources, which can generate on-demand a single particle state. It first outlines the electron optics formalism and its analogies and differences with photon optics and then turns to the presentation of single electron emitters and their characterization through the measurements of the average electrical current and its correlations. This is followed by a discussion of electron quantum optics experiments in the Hanbury-Brown and Twiss geometry where two-particle interferences occur. Finally, Coulomb interactions effects and their influence on single electron states are considered. (copyright 2013 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Electronic and optical properties of lead iodide

    DEFF Research Database (Denmark)

    Ahuja, R.; Arwin, H.; Ferreira da Silva, A.

    2002-01-01

    The electronic properties and the optical absorption of lead iodide (PbI2) have been investigated experimentally by means of optical absorption and spectroscopic ellipsometry, and theoretically by a full-potential linear muffin-tin-orbital method. PbI2 has been recognized as a very promising...

  20. Optical electronics self-organized integration and applications

    CERN Document Server

    Yoshimura, Tetsuzo

    2012-01-01

    IntroductionFrom Electronics to Optical ElectronicsAnalysis Tools for Optical CircuitsSelf-Organized Optical Waveguides: Theoretical AnalysisSelf-Organized Optical Waveguides: Experimental DemonstrationsOptical Waveguide Films with Vertical Mirrors 3-D Optical Circuits with Stacked Waveguide Films Heterogeneous Thin-Film Device IntegrationOptical Switches OE Hardware Built by Optical ElectronicsIntegrated Solar Energy Conversion SystemsFuture Challenges.

  1. Optics of Electron Beam in the Recycler

    International Nuclear Information System (INIS)

    Burov, A.; Kroc, T.; Lebedev, V.; Nagaitsev, S.; Prost, L.; Pruss, S.; Shemyakin, A.; Sutherland, M.; Warner, A.; Kazakevich, G.; Tiunov, M.

    2006-01-01

    Electron cooling of 8.9 GeV/c antiprotons in the Recycler ring (Fermilab) requires high current and good quality of the DC electron beam. Electron trajectories of ∼0.2 A or higher DC electron beam have to be parallel in the cooling section, within ∼ 0.2 mrad, making the beam envelope cylindrical. These requirements yielded a specific scheme of the electron transport from a gun to the cooling section, with electrostatic acceleration and deceleration in the Pelletron. Recuperation of the DC beam limits beam losses at as tiny level as ∼0.001%, setting strict requirements on the return electron line to the Pelletron and a collector. To smooth the beam envelope in the cooling section, it has to be linear and known at the transport start. Also, strength of the relevant optic elements has to be measured with good accuracy. Beam-based optic measurements are being carried out and analysed to get this information. They include beam simulations in the Pelletron, differential optic (beam response) measurements and simulation, beam profile measurements with optical transition radiation, envelope measurements and analysis with orifice scrapers. Current results for the first half-year of commissioning are presented. Although electron cooling is already routinely used for pbar stacking, its efficiency is expected to be improved

  2. Optimising electron microscopy experiment through electron optics simulation

    Energy Technology Data Exchange (ETDEWEB)

    Kubo, Y. [CEMES-CNRS, 29 Rue Jeanne Marvig, 31055 Toulouse France (France); Hitachi High-Technologies Corporation, 882, Ichige, Hitachinaka, Ibaraki 312-8504 (Japan); Gatel, C.; Snoeck, E. [CEMES-CNRS, 29 Rue Jeanne Marvig, 31055 Toulouse France (France); Houdellier, F., E-mail: florent.houdellier@cemes.fr [CEMES-CNRS, 29 Rue Jeanne Marvig, 31055 Toulouse France (France)

    2017-04-15

    We developed a new type of electron trajectories simulation inside a complete model of a modern transmission electron microscope (TEM). Our model incorporates the precise and real design of each element constituting a TEM, i.e. the field emission (FE) cathode, the extraction optic and acceleration stages of a 300 kV cold field emission gun, the illumination lenses, the objective lens, the intermediate and projection lenses. Full trajectories can be computed using magnetically saturated or non-saturated round lenses, magnetic deflectors and even non-cylindrical symmetry elements like electrostatic biprism. This multi-scale model gathers nanometer size components (FE tip) with parts of meter length (illumination and projection systems). We demonstrate that non-trivial TEM experiments requiring specific and complex optical configurations can be simulated and optimized prior to any experiment using such model. We show that all the currents set in all optical elements of the simulated column can be implemented in the real column (I2TEM in CEMES) and used as starting alignment for the requested experiment. We argue that the combination of such complete electron trajectory simulations in the whole TEM column with automatic optimization of the microscope parameters for optimal experimental data (images, diffraction, spectra) allows drastically simplifying the implementation of complex experiments in TEM and will facilitate the development of advanced use of the electron microscope in the near future. - Highlights: • Using dedicated electron optics software, we calculate full electrons trajectories inside a modern transmission electron microscope. • We have determined how to deal with multi-scale electron optics elements like high voltage cold field emission source. • W • e have succeed to model both weak and strong magnetic lenses whether in saturated or unsaturated conditions as well as electrostatic biprism and magnetic deflectors. • We have applied this model

  3. Optimising electron microscopy experiment through electron optics simulation

    International Nuclear Information System (INIS)

    Kubo, Y.; Gatel, C.; Snoeck, E.; Houdellier, F.

    2017-01-01

    We developed a new type of electron trajectories simulation inside a complete model of a modern transmission electron microscope (TEM). Our model incorporates the precise and real design of each element constituting a TEM, i.e. the field emission (FE) cathode, the extraction optic and acceleration stages of a 300 kV cold field emission gun, the illumination lenses, the objective lens, the intermediate and projection lenses. Full trajectories can be computed using magnetically saturated or non-saturated round lenses, magnetic deflectors and even non-cylindrical symmetry elements like electrostatic biprism. This multi-scale model gathers nanometer size components (FE tip) with parts of meter length (illumination and projection systems). We demonstrate that non-trivial TEM experiments requiring specific and complex optical configurations can be simulated and optimized prior to any experiment using such model. We show that all the currents set in all optical elements of the simulated column can be implemented in the real column (I2TEM in CEMES) and used as starting alignment for the requested experiment. We argue that the combination of such complete electron trajectory simulations in the whole TEM column with automatic optimization of the microscope parameters for optimal experimental data (images, diffraction, spectra) allows drastically simplifying the implementation of complex experiments in TEM and will facilitate the development of advanced use of the electron microscope in the near future. - Highlights: • Using dedicated electron optics software, we calculate full electrons trajectories inside a modern transmission electron microscope. • We have determined how to deal with multi-scale electron optics elements like high voltage cold field emission source. • W • e have succeed to model both weak and strong magnetic lenses whether in saturated or unsaturated conditions as well as electrostatic biprism and magnetic deflectors. • We have applied this model

  4. Electron-optical phonon coupling in superconductors

    International Nuclear Information System (INIS)

    Rietschel, H.

    1975-01-01

    The role of the optical phonons in superconductivity is investigated in the case of compounds with different atomic masses Msub(k). It is shown that the electron mass enhancement factor lambda is independent of Msub(k) if the force constant matrix is mass independent. However, when using lambda to calculate Tsub(c), it must be decomposed into its acoustical and optical contributions, which depend separately on Msub(k). Interference scattering from a light and a heavy mass is studied and its contributions to lambda within the free electron approximation. Numerical results are presented for a rocksalt structure crystal with nearest and next nearest neighbour coupling. These results indicate that the optical phonon contributions to lambda may substantially increase Tsub(c). (orig.) [de

  5. Electron-optical systems for Mott polarimeters

    International Nuclear Information System (INIS)

    Fishkova, T.Ya.; Mamaev, Yu.A.; Ovsyannikova, I.P.; Petrov, V.N.; Shpak, E.V.

    1994-01-01

    Electron-optical systems, forming polarized electron beams from solid and gaseous sources at a Mott detector with operating potentials of 20 and 50 kV, have been theoretically investigated. The integral EOS creates a beam <2.6 nm in diameter at the target of the Mott detector for secondary electrons with energies of 1-20 eV and exit angles of 0 -60 . The differential EOS provides an energy resolution of 2-6% within the range of 3-2000 eV, the illumination being 5-13% for a 4π angle; at the target of the Mott detector it creates a beam of 1-6 mm in diameter. Both systems have been constructed at the laboratory of Spin-polarized Electron Spectroscopy (Department of Experimental Physics) at St. Petersburg State Technical University. ((orig.))

  6. SLC polarized beam source electron optics design

    International Nuclear Information System (INIS)

    Eppley, K.R.; Lavine, T.L.; Early, R.A.; Herrmannsfeldt, W.B.; Miller, R.H.; Schultz, D.C.; Spencer, C.M.; Yeremian, A.D.

    1991-05-01

    This paper describes the design of the beam-line from the polarized electron gun to the linac injector in the Stanford Linear Collider (SLC). The polarized electron source is a GaAs photocathode, requiring 10 -11 -Torr-range pressure for adequate quantum efficiency and longevity. The photocathode is illuminated by 3-nsec-long laser pulses. The quality of the optics for the 160-kV beam is crucial since electron-stimulated gas desorption from beam loss in excess of 0.1% of the 20-nC pulses may poison the photocathode. Our design for the transport line consists of a differential pumping region isolated by a pair of valves. Focusing is provided by a pair of Helmholtz coils and by several iron-encased solenoidal lenses. Our optics design is based on beam transport simulations using 2 1/2-D particle-in-cell codes to model the gun and to solve the fully-relativistic time-dependent equations of motion in three dimensions for electrons in the presence of azimuthally symmetric electromagnetic fields. 6 refs., 6 figs

  7. On the optical stability of high-resolution transmission electron microscopes

    International Nuclear Information System (INIS)

    Barthel, J.; Thust, A.

    2013-01-01

    In the recent two decades the technique of high-resolution transmission electron microscopy experienced an unprecedented progress through the introduction of hardware aberration correctors and by the improvement of the achievable resolution to the sub-Ångström level. The important aspect that aberration correction at a given resolution requires also a well defined amount of optical stability has received little attention so far. Therefore we investigate the qualification of a variety of high-resolution electron microscopes to maintain an aberration corrected optical state in terms of an optical lifetime. We develop a comprehensive statistical framework for the estimation of the optical lifetime and find remarkably low values between tens of seconds and a couple of minutes. Probability curves are introduced, which inform the operator about the chance to work still in the fully aberration corrected state. - Highlights: • We investigate the temporal stability of optical aberrations in HRTEM. • We develop a statistical framework for the estimation of optical lifetimes. • We introduce plots showing the success probability for aberration-free work. • Optical lifetimes in sub-Ångström electron microscopy are surprisingly low. • The success of aberration correction depends strongly on the optical stability

  8. Electron optics with ballistic graphene junctions

    Science.gov (United States)

    Chen, Shaowen

    Electrons transmitted across a ballistic semiconductor junction undergo refraction, analogous to light rays across an optical boundary. A pn junction theoretically provides the equivalent of a negative index medium, enabling novel electron optics such as negative refraction and perfect (Veselago) lensing. In graphene, the linear dispersion and zero-gap bandstructure admit highly transparent pn junctions by simple electrostatic gating, which cannot be achieved in conventional semiconductors. Robust demonstration of these effects, however, has not been forthcoming. Here we employ transverse magnetic focusing to probe propagation across an electrostatically defined graphene junction. We find perfect agreement with the predicted Snell's law for electrons, including observation of both positive and negative refraction. Resonant transmission across the pn junction provides a direct measurement of the angle dependent transmission coefficient, and we demonstrate good agreement with theory. Comparing experimental data with simulation reveals the crucial role played by the effective junction width, providing guidance for future device design. Efforts toward sharper pn junction and possibility of zero field Veselago lensing will also be discussed. This work is supported by the Semiconductor Research Corporations NRI Center for Institute for Nanoelectronics Discovery and Exploration (INDEX).

  9. Hybrid electronic/optical synchronized chaos communication system.

    Science.gov (United States)

    Toomey, J P; Kane, D M; Davidović, A; Huntington, E H

    2009-04-27

    A hybrid electronic/optical system for synchronizing a chaotic receiver to a chaotic transmitter has been demonstrated. The chaotic signal is generated electronically and injected, in addition to a constant bias current, to a semiconductor laser to produce an optical carrier for transmission. The optical chaotic carrier is photodetected to regenerate an electronic signal for synchronization in a matched electronic receiver The system has been successfully used for the transmission and recovery of a chaos masked message that is added to the chaotic optical carrier. Past demonstrations of synchronized chaos based, secure communication systems have used either an electronic chaotic carrier or an optical chaotic carrier (such as the chaotic output of various nonlinear laser systems). This is the first electronic/optical hybrid system to be demonstrated. We call this generation of a chaotic optical carrier by electronic injection.

  10. Theory of optical spectra of solvated electrons

    International Nuclear Information System (INIS)

    Kestner, N.R.

    1975-01-01

    During the last few years better theoretical models of solvated electron have been developed. These models allow one to calculate a priori the observable properties of the trapped electron. One of the most important and most widely determined properties is the optical spectrum. In this paper we consider the predictions of the theories not only as to the band maximum but line shape and width. In addition we will review how the theories predict these will depend on the solvent, pressure, temperature, and solvent density. In all cases extensive comparisons will be made with experimental work. In addition four new areas will be explored and recent results will be presented. These concern electrons in dense polar gases, the time development of the solvated electron spectrum, solvated electrons in mixed solvents, and photoelectron emission spectra (PEE) as it relates to higher excited states. This paper will review all recent theoretical calculations and present a critical review of the present status and future developments which are anticipated. The best theories are quite successful in predicting trends, and qualitative agreement concerning band maximum. The theory is still weak in predicting line shape and line width

  11. Electron optical characteristics of a concave electrostatic electron mirror for a scanning electron microscope

    International Nuclear Information System (INIS)

    Hamarat, R.T.; Witzani, J.; Hoerl, E.M.

    1984-08-01

    Numerical computer calculations are used to explore the design characteristics of a concave electrostatic electron mirror for a mirror attachment for a conventional scanning electron microscope or an instrument designed totally as a scanning electron mirror microscope. The electron paths of a number of set-ups are calculated and drawn graphically in order to find the optimum shape and dimensions of the mirror geometry. This optimum configuration turns out to be the transition configuration between two cases of electron path deflection, towards the optical axis of the system and away from it. (Author)

  12. Particles and waves in electron optics and microscopy

    CERN Document Server

    Pozzi, Giulio

    2016-01-01

    Advances in Imaging and Electron Physics merges two long-running serials, Advances in Electronics and Electron Physics and Advances in Optical and Electron Microscopy. The series features extended articles on the physics of electron devices (especially semiconductor devices), particle optics at high and low energies, microlithography, image science, digital image processing, electromagnetic wave propagation, electron microscopy, and the computing methods used in all these domains. * Contains contributions from leading authorities on the subject matter* Informs and updates all the latest developments in the field of imaging and electron physics* Provides practitioners interested in microscopy, optics, image processing, mathematical morphology, electromagnetic fields, electron, and ion emission with a valuable resource* Features extended articles on the physics of electron devices (especially semiconductor devices), particle optics at high and low energies, microlithography, image science, and digital image pro...

  13. Numerical simulation methods for electron and ion optics

    International Nuclear Information System (INIS)

    Munro, Eric

    2011-01-01

    This paper summarizes currently used techniques for simulation and computer-aided design in electron and ion beam optics. Topics covered include: field computation, methods for computing optical properties (including Paraxial Rays and Aberration Integrals, Differential Algebra and Direct Ray Tracing), simulation of Coulomb interactions, space charge effects in electron and ion sources, tolerancing, wave optical simulations and optimization. Simulation examples are presented for multipole aberration correctors, Wien filter monochromators, imaging energy filters, magnetic prisms, general curved axis systems and electron mirrors.

  14. The theoretical study of the optical klystron free electron laser

    International Nuclear Information System (INIS)

    Yang Zhenhua

    2001-01-01

    The work of the theoretical study and numerical simulation of optical klystron free electron laser is supported by National 863 Research Development Program and National Science Foundation of China. The object of studying UV band free electron laser (FEL) is to understand the physical law of optical klystron FEL and to gain experience for design. A three-dimensional code OPFEL are made and it is approved that the code is correct completely. The magnetic field of the optical klystron, the energy modulation of the electron beam, the density modulation of the electron beam, spontaneous emission of the electron beam in optical klystron, the harmonic super-radiation of the electron beam, and the effects of the undulator magnetic field error on modulation of the electron beam energy are simulated. These results are useful for the future experiments

  15. Nonlinear optics with coherent free electron lasers

    Science.gov (United States)

    Bencivenga, F.; Capotondi, F.; Mincigrucci, R.; Cucini, R.; Manfredda, M.; Pedersoli, E.; Principi, E.; Simoncig, A.; Masciovecchio, C.

    2016-12-01

    We interpreted the recent construction of free electron laser (FELs) facilities worldwide as an unprecedented opportunity to bring concepts and methods from the scientific community working with optical lasers into the domain of x-ray science. This motivated our efforts towards the realization of FEL-based wave-mixing applications. In this article we present new extreme ultraviolet transient grating (X-TG) data from vitreous SiO2, collected using two crossed FEL pulses (photon frequency 38 eV) to generate the X-TG and a phase matched optical probing pulse (photon frequency 3.1 eV). This experiment extends our previous investigation, which was carried out on a nominally identical sample using a different FEL photon frequency (45 eV) to excite the X-TG. The present data are featured by a peak intensity of the X-TG signal substantially larger than that previously reported and by slower modulations of the X-TG signal at positive delays. These differences could be ascribed to the different FEL photon energy used in the two experiments or to differences in the sample properties. A systematic X-TG study on the same sample as a function of the FEL wavelength is needed to draw a consistent conclusion. We also discuss how the advances in the performance of the FELs, in terms of generation of fully coherent photon pulses and multi-color FEL emission, may push the development of original experimental strategies to study matter at the femtosecond-nanometer time-length scales, with the unique option of element and chemical state specificity. This would allow the development of advanced experimental tools based on wave-mixing processes, which may have a tremendous impact in the study of a large array of phenomena, ranging from nano-dynamics in complex materials to charge and energy transfer processes.

  16. Optical polarimeter based on Fourier analysis and electronic control

    International Nuclear Information System (INIS)

    Vilardy, J; Salas, V.; Torres, C.

    2016-01-01

    In this paper, we show the design and implementation of an optical polarimeter using electronic control and the Fourier analysis. The polarimeter prototype will be used as a main tool for the students of the Universidad Popular del Cesar that belong to the following university programs: Electronics engineering (optoelectronics area), Math and Physics degree and the Master in Physics Sciences, in order to learning the theory and experimental aspects of the state of optical polarization via the Stokes vector measurement. Using the electronic polarimeter proposed in this paper, the students will be able to observe (in an optical bench) and understand the different interactions of the states of optical polarization when the optical waves pass through to the polarizers and retarder waves plates. The electronic polarimeter has a software that captures the optical intensity measurement and evaluates the Stokes vector. (Author)

  17. Nonlinear fiber optics formerly quantum electronics

    CERN Document Server

    Agrawal, Govind

    1995-01-01

    The field of nonlinear fiber optics has grown substantially since the First Edition of Nonlinear Fiber Optics, published in 1989. Like the First Edition, this Second Edition is a comprehensive, tutorial, and up-to-date account of nonlinear optical phenomena in fiber optics. It synthesizes widely scattered research material and presents it in an accessible manner for students and researchers already engaged in or wishing to enter the field of nonlinear fiber optics. Particular attention is paid to the importance of nonlinear effects in the design of optical fiber communication systems. This is

  18. Integrated optical transceiver with electronically controlled optical beamsteering

    Science.gov (United States)

    Davids, Paul; DeRose, Christopher; Tauke-Pedretti, Anna

    2017-08-22

    A beam-steering optical transceiver is provided. The transceiver includes one or more modules, each comprising an antenna chip and a control chip bonded to the antenna chip. Each antenna chip has a feeder waveguide, a plurality of row waveguides that tap off from the feeder waveguide, and a plurality of metallic nanoantenna elements arranged in a two-dimensional array of rows and columns such that each row overlies one of the row waveguides. Each antenna chip also includes a plurality of independently addressable thermo-optical phase shifters, each configured to produce a thermo-optical phase shift in a respective row. Each antenna chip also has, for each row, a row-wise heating circuit configured to produce a respective thermo-optic phase shift at each nanoantenna element along its row. The control chip includes controllable current sources for the independently addressable thermo-optical phase shifters and the row-wise heating circuits.

  19. PREVAIL-EPL alpha tool electron optics subsystem

    Science.gov (United States)

    Pfeiffer, Hans C.; Dhaliwal, Rajinder S.; Golladay, Steven D.; Doran, Samuel K.; Gordon, Michael S.; Kendall, Rodney A.; Lieberman, Jon E.; Pinckney, David J.; Quickle, Robert J.; Robinson, Christopher F.; Rockrohr, James D.; Stickel, Werner; Tressler, Eileen V.

    2001-08-01

    The IBM/Nikon alliance is continuing pursuit of an EPL stepper alpha tool based on the PREVAIL technology. This paper provides a status report of the alliance activity with particular focus on the Electron Optical Subsystem developed at IBM. We have previously reported on design features of the PREVAIL alpha system. The new state-of-the-art e-beam lithography concepts have since been reduced to practice and turned into functional building blocks of a production level lithography tool. The electron optical alpha tool subsystem has been designed, build, assembled and tested at IBM's Semiconductor Research and Development Center (SRDC) in East Fishkill, New York. After demonstrating subsystem functionality, the electron optical column and all associated control electronics hardware and software have been shipped during January 2001 to Nikon's facility in Kumagaya, Japan, for integration into the Nikon commercial e-beam stepper alpha tool. Early pre-shipment results obtained with this electron optical subsystem are presented.

  20. Density functional study of : Electronic and optical properties

    Indian Academy of Sciences (India)

    K C Bhamu

    3Department of Physics, Swami Keshvanand Insitute of Technology, Management and Gramothan, ... Published online 20 June 2017. Abstract. This paper focusses on the electronic and optical properties of scandium-based silver delafossite.

  1. Electron Optics for Biologists: Physical Origins of Spherical Aberrations

    Science.gov (United States)

    Geissler, Peter; Zadunaisky, Jose

    1974-01-01

    Reports on the physical origins of spherical aberrations in axially symmetric electrostatic lenses to convey the essentials of electon optics to those who must think critically about the resolution of the electron microscope. (GS)

  2. First-principle calculations of structural, electronic, optical, elastic ...

    Indian Academy of Sciences (India)

    S CHEDDADI

    2017-11-28

    Nov 28, 2017 ... First-principle calculations on the structural, electronic, optical, elastic and thermal properties of the chalcopyrite ... The Kohn–Sham equations were solved using the ... RMTKmax = 7 was used for all the investigated systems,.

  3. Electronic structure and optical properties of solid C60

    International Nuclear Information System (INIS)

    Mattesini, M.; Ahuja, R.; Sa, L.; Hugosson, H.W.; Johansson, B.; Eriksson, O.

    2009-01-01

    The electronic structure and the optical properties of face-centered-cubic C 60 have been investigated by using an all-electron full-potential method. Our ab initio results show that the imaginary dielectric function for high-energy values looks very similar to that of graphite, revealing close electronic structure similarities between the two systems. We have also identified the origin of different peaks in the dielectric function of fullerene by means of the calculated electronic density of states. The computed optical spectrum compares fairly well with the available experimental data for the Vis-UV absorption spectrum of solid C 60 .

  4. DNA Diagnostics: Optical or by Electronics?

    KAUST Repository

    Khan, Hadayat Ullah; Knoll, Wolfgang

    2016-01-01

    In this paper, we very briefly review DNA biosensors based on optical and electrical detection principles, referring mainly to our past work applying both techniques but here using nearly identical sensor chip surface architectures, i.e., capture

  5. Anomalous optical and electronic properties of dense sodium

    International Nuclear Information System (INIS)

    Li Dafang; Liu Hanyu; Wang Baotian; Shi Hongliang; Zhu Shaoping; Yan Jun; Zhang Ping

    2010-01-01

    Based on the density functional theory, we systematically study the optical and electronic properties of the insulating dense sodium phase (Na-hp4) reported recently (Ma et al., 2009). The structure is found optically anisotropic. Through Bader analysis, we conclude that ionicity exists in the structure and becomes stronger with increasing pressure.

  6. Electron cascades in sensors for optical detection of ionizing radiation

    International Nuclear Information System (INIS)

    London, Richard A.; Lowry, Mark E.; Vernon, Stephen P.; Stewart, Richard E.

    2013-01-01

    A new class of high-speed detectors, called RadOptic detectors, measures ionizing radiation incident on a transparent semiconductor by sensing changes in the refractive index with an optical probe beam. We describe the role of radiation-initiated electron cascades in setting the sensitivity and the spatial and temporal resolution of RadOptic detectors. We model electron cascades with both analytical and Monte Carlo computational methods. We find that the timescale for the development of an electron cascade is less than of order 100 fs and is not expected to affect the time response of a detector. The characteristic size of the electron cloud is typically less than 2 μm, enabling high spatial resolution in imaging systems. The electron-hole pair density created by single x-rays is much smaller than the saturation density and, therefore, single events should not saturate the detector

  7. Surprising quantum bounces

    CERN Document Server

    Nesvizhevsky, Valery

    2015-01-01

    This unique book demonstrates the undivided unity and infinite diversity of quantum mechanics using a single phenomenon: quantum bounces of ultra-cold particles. Various examples of such "quantum bounces" are: gravitational quantum states of ultra-cold neutrons (the first observed quantum states of matter in a gravitational field), the neutron whispering gallery (an observed matter-wave analog of the whispering gallery effect well known in acoustics and for electromagnetic waves), and gravitational and whispering gallery states for anti-matter atoms that remain to be observed. These quantum states are an invaluable tool in the search for additional fundamental short-range forces, for exploring the gravitational interaction and quantum effects of gravity, for probing physics beyond the standard model, and for furthering studies into the foundations of quantum mechanics, quantum optics, and surface science.

  8. Comparison of optical and electron spectra in an infra-red free electron laser

    Energy Technology Data Exchange (ETDEWEB)

    MacLeod, A.M.; Gillespie, W.A.; Martin, P.F. [Univ. of Abertay, Dundee (United Kingdom)] [and others

    1995-12-31

    Time-resolved electron and optical spectra recently acquired at the FELIX facility are presented, showing the evolution of the respective macropulses. A comparison is made between the optical power output during the macropulse and the measured power extracted from the electron beam using a simple model of the cavity losses. Data are available for a wide range of operating conditions: the wavelength range is from 9 {mu}m to 28 {mu}m and detuning are between 1/4{lambda} and 2{lambda}. The effect of rapid electron beam energy changes on the optical and electron spectra will also be discussed.

  9. Optical Biosensors: A Revolution Towards Quantum Nanoscale Electronics Device Fabrication

    Directory of Open Access Journals (Sweden)

    D. Dey

    2011-01-01

    Full Text Available The dimension of biomolecules is of few nanometers, so the biomolecular devices ought to be of that range so a better understanding about the performance of the electronic biomolecular devices can be obtained at nanoscale. Development of optical biomolecular device is a new move towards revolution of nano-bioelectronics. Optical biosensor is one of such nano-biomolecular devices that has a potential to pave a new dimension of research and device fabrication in the field of optical and biomedical fields. This paper is a very small report about optical biosensor and its development and importance in various fields.

  10. Ultrafast electron diffraction studies of optically excited thin bismuth films

    International Nuclear Information System (INIS)

    Rajkovic, Ivan

    2008-01-01

    This thesis contains work on the design and the realization of an experimental setup capable of providing sub-picosecond electron pulses for ultrafast electron diffraction experiments, and performing the study of ultrafast dynamics in bismuth after optical excitation using this setup. (orig.)

  11. Ultrafast electron diffraction studies of optically excited thin bismuth films

    Energy Technology Data Exchange (ETDEWEB)

    Rajkovic, Ivan

    2008-10-21

    This thesis contains work on the design and the realization of an experimental setup capable of providing sub-picosecond electron pulses for ultrafast electron diffraction experiments, and performing the study of ultrafast dynamics in bismuth after optical excitation using this setup. (orig.)

  12. Optical plasma torch electron bunch generation in plasma wakefield accelerators

    Directory of Open Access Journals (Sweden)

    G. Wittig

    2015-08-01

    Full Text Available A novel, flexible method of witness electron bunch generation in plasma wakefield accelerators is described. A quasistationary plasma region is ignited by a focused laser pulse prior to the arrival of the plasma wave. This localized, shapeable optical plasma torch causes a strong distortion of the plasma blowout during passage of the electron driver bunch, leading to collective alteration of plasma electron trajectories and to controlled injection. This optically steered injection is more flexible and faster when compared to hydrodynamically controlled gas density transition injection methods.

  13. Electron-Beam Produced Air Plasma: Optical and Electrical Diagnostics

    Science.gov (United States)

    Vidmar, Robert; Stalder, Kenneth; Seeley, Megan

    2006-10-01

    High energy electron impact excitation is used to stimulate optical emissions that quantify the measurement of electron beam current. A 100 keV 10-ma electron beam source is used to produce air plasma in a test cell at a pressure between 1 mTorr and 760 Torr. Optical emissions originating from the N2 2^nd positive line at 337.1 nm and the N2^+ 1^st negative line at 391.4 nm are observed. Details on calibration using signals from an isolated transmission window and a Faraday plate are discussed. Results using this technique and other electrical signal are presented.

  14. Optical studies of polarized-electron-noble-gas collisions

    International Nuclear Information System (INIS)

    Gay, T.I.; Furst, J.E.; Geesmann, H.; Khakoo, M.A.; Madison, D.H.; Wijayaratna, W.M.K.P.; Bartschat, K.

    1992-01-01

    We have measured the Stoke's parameters of light emitted following impact excitation of He and Xe by transversely-polarized electrons. For He, the 2 3 S-3 3 P, 389 nm transition was studied in an effort to systematically develop a highly accurate optical electron polarimeter. The 6 3 P 2 -6 3 D 3 , 882 nm transition in Xe was used to assess the importance of spin-dependent forces on the continuum electron for this target. We attempted (and failed) to made the first optical observations of Mott scattering. (Author)

  15. Interference electron microscopy of one-dimensional electron-optical phase objects

    International Nuclear Information System (INIS)

    Fazzini, P.F.; Ortolani, L.; Pozzi, G.; Ubaldi, F.

    2006-01-01

    The application of interference electron microscopy to the investigation of electron optical one-dimensional phase objects like reverse biased p-n junctions and ferromagnetic domain walls is considered. In particular the influence of diffraction from the biprism edges on the interference images is analyzed and the range of applicability of the geometric optical equation for the interpretation of the interference fringe shifts assessed by comparing geometric optical images with full wave-optical simulations. Finally, the inclusion of partial spatial coherence effects are discussed

  16. Electron beams, lenses, and optics. Volume 2

    International Nuclear Information System (INIS)

    El-Kareh, A.B.; El-Kareh, J.C.J.

    1970-01-01

    This volume presents a systematic coverage of aberrations. It analyzes the geometrical aberrations and treats the spherical and chromatic aberrations in great detail. The coefficients of spherical and chromatic aberration have been computed for a series of electrostatic and magnetic lenses and are listed in table form. The book also covers space charge and its effect on highly focused electron beams

  17. Electron Correlation Models for Optical Activity

    DEFF Research Database (Denmark)

    Höhn, E. G.; O. E. Weigang, Jr.

    1968-01-01

    A two-system no-overlap model for rotatory strength is developed for electric-dipole forbidden as well as allowed transitions. General equations which allow for full utilization of symmetry in the chromophore and in the environment are obtained. The electron correlation terms are developed in full...

  18. DNA Diagnostics: Optical or by Electronics?

    KAUST Repository

    Khan, Hadayat Ullah

    2016-01-15

    In this paper, we very briefly review DNA biosensors based on optical and electrical detection principles, referring mainly to our past work applying both techniques but here using nearly identical sensor chip surface architectures, i.e., capture probe layers that were prepared based on a pulsed plasma deposition protocol for maleic anhydride and subsequent wet-chemical attachment of the amine-functionalized peptide nucleic acid (PNA) probe oligonucleotides. 15 mer DNA target strands, labeled with Cy5-chromophores that were attached at the 5’ end were used for surface plasmon optical detection and the same target DNA but without label was used in OTFT sensor-based detection where the mere charge density of the bound (hybridized) DNA molecules modulate the source-drain current. The sensing mechanisms and the detection limits of the devices are described in some detail. Both techniques allow for the monitoring of surface hybridization reactions, and offer the capacity to quantitatively discriminate between targets with different degrees of mismatched sequences.

  19. Polarized electrons and the origin of optical activity

    International Nuclear Information System (INIS)

    Bonner, W.A.; Dort, M.A. Van; Yearian, M.R.; Zeman, H.D.; Li, G.C.; Stanford Univ., Calif.

    1976-01-01

    The history of experiments bearing on the origin of optical acitivity in nature by parity non-conservation during the β-decay of radioactive isotopes is briefly reviewed. Following this, we present a more detailed description of our recent published and unpublished data and calculations regarding the generation of optical activity in DL-leucine by means of artificially produced longitudinally polarized electrons from a linear accelerator

  20. Electron beam optics for the FEL experiment and IFEL experiment

    International Nuclear Information System (INIS)

    van Steenbergen, A.

    1990-01-01

    Electron beam transport system parameters for the FEL experiment and for the FEL experiment are given. The perturbation of the ''interaction region'' optics due to wiggler focussing is taken into account and a range of solutions are provided for relevant Twiss parameters in the FEL or IFEL region. Modifications of the transport optics in specific sections of the overall beam transport lines, for reasons of enhanced diagnostic capability or enhanced beam momentum analysis resolution, is also presented

  1. Optical guiding and beam bending in free-electron lasers

    International Nuclear Information System (INIS)

    Scharlemann, E.T.

    1987-01-01

    The electron beam in a free-electron laser (FEL) can act as an optical fiber, guiding or bending the optical beam. The refractive and gain effects of the bunched electron beam can compensate for diffraction, making possible wigglers that are many Rayleigh ranges (i.e., characteristic diffraction lengths) long. The origin of optical guiding can be understood by examining gain and refractive guiding in a fiber with a complex index of refraction, providing a mathematical description applicable also to the FEL, with some extensions. In the exponential gain regime of the FEL, the electron equations of motion must be included, but a self-consistent description of exponential gain with diffraction fully included becomes possible. The origin of the effective index of refraction of an FEL is illustrated with a simple example of bunched, radiating dipoles. Some of the properties of the index of refraction are described. The limited experimental evidence for optical beam bending is summarized. The evidence does not yet provide conclusive proof of the existence of optical guiding, but supports the idea. Finally, the importance of refractive guiding for the performance of a high-gain tapered-wiggler FEL amplifier is illustrated with numerical simulations

  2. Optical distortions in electron/positron storage rings

    International Nuclear Information System (INIS)

    Brown, K.L.; Donald, M.; Servranckx, R.

    1983-01-01

    We have studied the optical distortions in the PEP electron/positron storage ring for various optical configurations using the computer programs DIMAT, HARMON, PATRICIA, and TURTLE. The results are shown graphically by tracing several thousand trajectories from one interaction region to the next using TURTLE and by tracing a few selected rays several hundred turns using the programs DIMAT and PATRICIA. The results show an interesting correlation between the calculated optical cleanliness of a particular lattice configuration and the observed operating characteristics of the machine

  3. New fiber optics illumination system for application to electronics holography

    Science.gov (United States)

    Sciammarella, Cesar A.

    1995-08-01

    The practical application of electronic holography requires the use of fiber optics. The need of employing coherent fiber optics imposes restrictions in the efficient use of laser light. This paper proposes a new solution to this problem. The proposed method increases the efficiency in the use of the laser light and simplifies the interface between the laser source and the fiber optics. This paper will present the theory behind the proposed method. A discussion of the effect of the different parameters that influence the formation of interference fringes is presented. Limitations and results that can be achieved are given. An example of application is presented.

  4. Optical-potential model for electron-atom scattering

    International Nuclear Information System (INIS)

    Callaway, J.; Oza, D.H.

    1985-01-01

    It is proposed that the addition of a matrix optical potential to a close-coupling calculation should lead to improved results in studies of electron-atom scattering. This procedure is described with use of a pseudostate expansion to evaluate the optical potential. The integro-differential equations are solved by a linear-algebraic method. As a test case, applications are made to electron-hydrogen scattering, and the results are compared with those obtained by other calculational procedures, and with experiment

  5. Characterization of nanocrystalline zirconia powders by electron optical techniques

    International Nuclear Information System (INIS)

    Bursill, L.A.

    1989-01-01

    Electron optical techniques are described for the characterization of the size distribution of agglomerates, aggregates and primary micro- and nanocrystallites of as-processed zirconia powders. These techniques allow for direct identification of individual crystallites as tetragonal or monoclinic, by optical transform of high-resolution electron micrographs. The latter also permit surface morphology to be examined with atomic resolution. Applications to a range of pure and doped zirconia powders, of recent commercial interest, are presented, which enable the results of concurrent studies by sedimentation, surface specific area measurements, porosity and sinterability to be correctly interpreted. 18 figs

  6. Optical and electron microanalysis of cuprate superconductors

    International Nuclear Information System (INIS)

    Hoff, H.A.; Osofsky, M.S.; Toth, L.E.; Richards, L.E.; Pande, C.S.; Lechter, W.L.

    1990-01-01

    Individual anisotropic grains in heterogeneous and opaque cuprate materials, when viewed in a reflected-light optical microscope through crossed polarizers, often have characteristic colors, when a daylight source is used. Of the cuprate superconductors, regardless of charge carrier type, examined so far, only one characteristic color has been observed We have studied the presence of color and found a strong correlation with the existence of superconductivity. The change in color from insulator to metal to superconductor and the compositions corresponding to these changes found by quantitative energy dispersive x-ray spectroscopy on superconducting Tl-Sr-Ca-Cu-O and metallic but not superconducting La-Sr-Cu-O materials is discussed

  7. Surprise... Surprise..., An Empirical Investigation on How Surprise is Connected to Customer Satisfaction

    NARCIS (Netherlands)

    J. Vanhamme (Joëlle)

    2003-01-01

    textabstractThis research investigates the specific influence of the emotion of surprise on customer transaction-specific satisfaction. Four empirical studies-two field studies (a diary study and a cross section survey) and two experiments-were conducted. The results show that surprise positively

  8. Fiber optic probe of free electron evanescent fields in the optical frequency range

    Energy Technology Data Exchange (ETDEWEB)

    So, Jin-Kyu, E-mail: js1m10@orc.soton.ac.uk; MacDonald, Kevin F. [Optoelectronics Research Centre and Centre for Photonic Metamaterials, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); Zheludev, Nikolay I. [Optoelectronics Research Centre and Centre for Photonic Metamaterials, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); Centre for Disruptive Photonic Technologies, Nanyang Technological University, Singapore 637371 (Singapore)

    2014-05-19

    We introduce an optical fiber platform which can be used to interrogate proximity interactions between free-electron evanescent fields and photonic nanostructures at optical frequencies in a manner similar to that in which optical evanescent fields are sampled using nanoscale aperture probes in scanning near-field microscopy. Conically profiled optical fiber tips functionalized with nano-gratings are employed to couple electron evanescent fields to light via the Smith-Purcell effect. We demonstrate the interrogation of medium energy (30–50 keV) electron fields with a lateral resolution of a few micrometers via the generation and detection of visible/UV radiation in the 700–300 nm (free-space) wavelength range.

  9. Electron optics development for photo-electron spectrometers

    Energy Technology Data Exchange (ETDEWEB)

    Wannberg, Bjoern [VG Scienta AB, P.O. Box 15120, SE-750 15 Uppsala (Sweden); BW Particle Optics AB, P.O. Box 55, SE-822 22 Alfta (Sweden)], E-mail: bjorn@particleoptics.se

    2009-03-21

    The demand for simultaneous observation of photo-electron distributions in several dimensions has made the hemispherical deflection analyzer (HDA) and the time-of-flight (TOF) analyzer the dominating spectrometer types. Some common limiting factors for resolution and sensitivity are considered. Recent developments of the HDA and its lens system which increase the energy range and angular acceptance are described. The properties of a recently developed angle-resolving TOF system (AR-TOF) are also described. The possibility to avoid integration losses in energy or angular resolution by applying non-linear mappings of the primary data is discussed.

  10. Electron optics development for photo-electron spectrometers

    International Nuclear Information System (INIS)

    Wannberg, Bjoern

    2009-01-01

    The demand for simultaneous observation of photo-electron distributions in several dimensions has made the hemispherical deflection analyzer (HDA) and the time-of-flight (TOF) analyzer the dominating spectrometer types. Some common limiting factors for resolution and sensitivity are considered. Recent developments of the HDA and its lens system which increase the energy range and angular acceptance are described. The properties of a recently developed angle-resolving TOF system (AR-TOF) are also described. The possibility to avoid integration losses in energy or angular resolution by applying non-linear mappings of the primary data is discussed.

  11. Structure, Electronic and Nonlinear Optical Properties of Furyloxazoles and Thienyloxazoles

    International Nuclear Information System (INIS)

    Dagli, Ozlem; Gok, Rabia; Bahat, Mehmet; Ozbay, Akif

    2016-01-01

    Geometry optimization, electronic and nonlinear optical properties of isomers of furyloxazole and thienyloxazole molecules are carried out at the B3LYP/6-311++G(2d,p) level. The conformational analysis of 12 compounds have been studied as a function of torsional angle between rings. Electronic and NLO properties such as dipole moment, energy gap, polarizability and first hyperpolarizability were also calculated. (paper)

  12. Optical properties and electron transport in low-dimensional nanostructures

    Czech Academy of Sciences Publication Activity Database

    Král, Karel; Menšík, Miroslav

    2011-01-01

    Roč. 54, 2-2 (2011), s. 4-13 ISSN 0021-3411 R&D Projects: GA MŠk(CZ) OC10007 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z40500505 Keywords : quantum dots * electron -photon interaction * optical properties * electron relaxation * DNA molecule Subject RIV: BE - The oretical Physics http://elibrary.ru/contents.asp?issueid=1010336

  13. Examples of electrostatic electron optics: The Farrand and Elektros microscopes and electron mirrors

    International Nuclear Information System (INIS)

    Hawkes, P.W.

    2012-01-01

    The role of Gertrude Rempfer in the design of the Farrand and Elektros microscopes is evoked. The study of electron mirror optics, aberration correction using mirrors and the development of microscopes employing electron mirrors are recapitulated, accompanied by a full bibliography, of earlier publications in particular.

  14. The structural design and the electron optics of a hybrid electron-ion gun

    International Nuclear Information System (INIS)

    Bas, E.B.; Gisler, E.; Stucki, F.

    1984-01-01

    This paper describes a new kind of a particle gun called the hybrid gun. It is able to deliver a finely focused electron or ion beam simply by reversing the polarity of the acceleration voltage. The detailed design features of the gun are given and the electron-ion optical properties are discussed. (author)

  15. Electronic displays using optically pumped luminescent semiconductor nanocrystals

    Science.gov (United States)

    Weiss, Shimon [Pinole, CA; Schlamp, Michael C [Plainsboro, NJ; Alivisatos, A Paul [Oakland, CA

    2011-09-27

    A multicolor electronic display is based on an array of luminescent semiconductor nanocrystals. Nanocrystals which emit light of different colors are grouped into pixels. The nanocrystals are optically pumped to produce a multicolor display. Different sized nanocrystals are used to produce the different colors. A variety of pixel addressing systems can be used.

  16. Structural, elastic, electronic and optical properties of bi-alkali ...

    Indian Academy of Sciences (India)

    The structural parameters, elastic constants, electronic and optical properties of the bi-alkali ... and efficient method for the calculation of the ground-state ... Figure 2. Optimization curve (E–V) of the bi-alkali antimonides: (a) Na2KSb, (b) Na2RbSb, (c) Na2CsSb, .... ical shape of the charge distributions in the contour plots.

  17. Electronic structure and optical properties of thorium monopnictides

    Indian Academy of Sciences (India)

    Unknown

    Indian Academy of Sciences. 165. Electronic structure and optical properties of thorium monopnictides. S KUMAR* and S AULUCK†. Physics Department, Institute of Engineering and Technology, M.J.P. Rohilkhand University, Bareilly 243 006,. India. †Department of Physics, Indian Institute of Technology, Roorkee 247 667, ...

  18. Applied nonlinear optics in the journal 'Quantum Electronics'

    International Nuclear Information System (INIS)

    Grechin, Sergei G; Dmitriev, Valentin G; Chirkin, Anatolii S

    2011-01-01

    A brief historical review of the experimental and theoretical works on nonlinear optical frequency conversion (generation of harmonics, up- and down-conversion, parametric oscillation), which have been published in the journal 'Quantum Electronics' for the last 40 years, is presented.

  19. Optical klystron and harmonic generation free electron laser

    Directory of Open Access Journals (Sweden)

    Qika Jia

    2005-06-01

    Full Text Available The optical field evolution of an optical klystron free electron laser is analytically described for both low gain and high gain cases. The harmonic optical klystron (HOK in which the second undulator is resonant on the higher harmonic of the first undulator is analyzed as a harmonic amplifier. The optical field evolution equation of the HOK is derived analytically for both the CHG mode (coherent harmonic generation, the quadratic gain regime and the HGHG mode (high gain harmonic generation, the exponential gain regime, the effects of energy spread, energy modulation, and dispersion in the whole process are taken into account. The linear theory is given and discussed for the HGHG mode. The analytical formula is given for the CHG mode.

  20. Electronic properties of wurtzite-phase InP nanowires determined by optical and magneto-optical spectroscopy

    Science.gov (United States)

    De Luca, Marta; Polimeni, Antonio

    2017-12-01

    Thanks to their peculiar shape and dimensions, semiconductor nanowires (NWs) are emerging as building components of novel devices. The presence of wurtzite (WZ) phase in the lattice structure of non-nitride III-V NWs is one of the most surprising findings in these nanostructures: this phase, indeed, cannot be found in the same materials in the bulk form, where the zincblende (ZB) structure is ubiquitous, and therefore the WZ properties are poorly known. This review focuses on WZ InP NWs, because growth techniques have reached a high degree of control on the structural properties of this material, and optical studies performed on high-quality samples have allowed determining the most useful electronic properties, which are reviewed here. After an introduction summarizing the reasons for the interest in WZ InP nanowires (Sec. I), we give an overview on growth process and structural and optical properties of WZ InP NWs (Sec. II). In Sec. III, a complete picture of the energy and symmetry of the lowest-energy conduction and valence bands, as assessed by polarization-resolved photoluminescence (PL) and photoluminescence-excitation (PLE) studies is drawn and compared to all the available theoretical information. The elastic properties of WZ InP (determined by PL under hydrostatic pressure) and the radiative recombination dynamics of spatially direct and indirect (namely, occurring across the WZ/ZB interfaces) transitions are also discussed. Section IV, focuses on the magneto-optical studies of WZ InP NWs. The diagram of the energy levels of excitons in WZ materials—with and without magnetic field—is first provided. Then, all theoretical and experimental information available about the changes in the transport properties (i.e., carrier effective mass) caused by the ZB→WZ phase variation are reviewed. Different NW/magnetic field geometrical configurations, sensitive to polarization selection rules, highlight anisotropies in the diamagnetic shifts, Zeeman splitting

  1. Future opportunities in production of disposable optics and electronics

    Science.gov (United States)

    Korhonen, Raimo

    2001-05-01

    The several production methods of paper processing chain can be used, by analogy, to generate novel ideas for production of optics and electronics. Paper processing is a very fast reel-to-reel process: In the beginning of the paper web production the process is running at the speed of over thousand meters per minute and the web width can be 10 meters, and still at the later stages the speed is several hundreds of meters per minute with the web width of a couple of meters. There are several potential reel-to-reel production methods like embossing, printing, laminating and different kinds of vacuum coating, for example evaporation and sputtering. End products are complex multi-layer composite structures. The benefits from this analogy for optics and electronics would be ideas for ultra fast production, paper-like disposable and recyclable products and the integration of optics and electronics into ordinary things like books, wallpapers, tissue papers and packages. Two experiments are presented to demonstrate the possibilities. In the first experiment optical patterns are embossed directly on paper. In the second one conductive polymers are printed on paper and plastic webs. In future, a wide network of cooperation will be needed to realize all the opportunities.

  2. Electronic properties and optical absorption of a phosphorene quantum dot

    Science.gov (United States)

    Liang, F. X.; Ren, Y. H.; Zhang, X. D.; Jiang, Z. T.

    2018-03-01

    Using the tight-binding Hamiltonian approach, we theoretically study the electronic and optical properties of a triangular phosphorene quantum dot (PQD) including one normal zigzag edge and two skewed armchair edges (ZAA-PQD). It is shown that the energy spectrum can be classified into the filled band (FB), the zero-energy band (ZB), and the unfilled band (UB). Numerical calculations of the FB, ZB, and UB probability distributions show that the FB and the UB correspond to the bulk states, while the ZB corresponds to the edge states, which appear on all of the three edges of the ZAA-PQD sharply different from the other PQDs. We also find that the strains and the electric fields can affect the energy levels inhomogeneously. Then the optical properties of the ZAA-PQD are investigated. There appear some strong low-energy optical absorption peaks indicating its sensitive low-energy optical response that is absent in other PQDs. Moreover, the strains and the electric fields can make inhomogeneous influences on the optical spectrum of the ZAA-PQD. This work may provide a useful reference for designing the electrical, mechanical, and optical PQD devices.

  3. Study of optical and electronic properties of nickel from reflection electron energy loss spectra

    Science.gov (United States)

    Xu, H.; Yang, L. H.; Da, B.; Tóth, J.; Tőkési, K.; Ding, Z. J.

    2017-09-01

    We use the classical Monte Carlo transport model of electrons moving near the surface and inside solids to reproduce the measured reflection electron energy-loss spectroscopy (REELS) spectra. With the combination of the classical transport model and the Markov chain Monte Carlo (MCMC) sampling of oscillator parameters the so-called reverse Monte Carlo (RMC) method was developed, and used to obtain optical constants of Ni in this work. A systematic study of the electronic and optical properties of Ni has been performed in an energy loss range of 0-200 eV from the measured REELS spectra at primary energies of 1000 eV, 2000 eV and 3000 eV. The reliability of our method was tested by comparing our results with the previous data. Moreover, the accuracy of our optical data has been confirmed by applying oscillator strength-sum rule and perfect-screening-sum rule.

  4. Quantum entanglement in electron optics generation, characterization, and applications

    CERN Document Server

    Chandra, Naresh

    2013-01-01

    This monograph forms an interdisciplinary study in atomic, molecular, and quantum information (QI) science. Here a reader will find that applications of the tools developed in QI provide new physical insights into electron optics as well as properties of atoms & molecules which, in turn, are useful in studying QI both at fundamental and applied levels. In particular, this book investigates entanglement properties of flying electronic qubits generated in some of the well known processes capable of taking place in an atom or a molecule following the absorption of a photon. Here, one can generate Coulombic or fine-structure entanglement of electronic qubits. The properties of these entanglements differ not only from each other, but also from those when spin of an inner-shell photoelectron is entangled with the polarization of the subsequent fluorescence. Spins of an outer-shell electron and of a residual photoion can have free or bound entanglement in a laboratory.

  5. Optical Performance of Carbon-Nanotube Electron Sources

    International Nuclear Information System (INIS)

    Jonge, Niels de; Allioux, Myriam; Oostveen, Jim T.; Teo, Kenneth B. K.; Milne, William I.

    2005-01-01

    The figure of merit for the electron optical performance of carbon-nanotube (CNT) electron sources is presented. This figure is given by the relation between the reduced brightness and the energy spread in the region of stable emission. It is shown experimentally that a CNT electron source exhibits a highly stable emission process that follows the Fowler-Nordheim theory for field emission, fixing the relationship among the energy spread, the current, and the radius. The performance of the CNT emitter under realistic operating conditions is compared with state-of-the-art electron point sources. It is demonstrated that the reduced brightness is a function of the tunneling parameter, a measure of the energy spread at low temperatures, only, independent of the geometry of the emitter

  6. Materials and Reliability Handbook for Semiconductor Optical and Electron Devices

    CERN Document Server

    Pearton, Stephen

    2013-01-01

    Materials and Reliability Handbook for Semiconductor Optical and Electron Devices provides comprehensive coverage of reliability procedures and approaches for electron and photonic devices. These include lasers and high speed electronics used in cell phones, satellites, data transmission systems and displays. Lifetime predictions for compound semiconductor devices are notoriously inaccurate due to the absence of standard protocols. Manufacturers have relied on extrapolation back to room temperature of accelerated testing at elevated temperature. This technique fails for scaled, high current density devices. Device failure is driven by electric field or current mechanisms or low activation energy processes that are masked by other mechanisms at high temperature. The Handbook addresses reliability engineering for III-V devices, including materials and electrical characterization, reliability testing, and electronic characterization. These are used to develop new simulation technologies for device operation and ...

  7. Pseudorandom binary injection of levitons for electron quantum optics

    Science.gov (United States)

    Glattli, D. C.; Roulleau, P.

    2018-03-01

    The recent realization of single-electron sources lets us envision performing electron quantum optics experiments, where electrons can be viewed as flying qubits propagating in a ballistic conductor. To date, all electron sources operate in a periodic electron injection mode, leading to energy spectrum singularities in various physical observables which sometimes hide the bare nature of physical effects. To go beyond this, we propose a spread-spectrum approach where electron flying qubits are injected in a nonperiodic manner following a pseudorandom binary bit pattern. Extending the Floquet scattering theory approach from periodic to spread-spectrum drive, the shot noise of pseudorandom binary sequences of single-electron injection can be calculated for leviton and nonleviton sources. Our new approach allows us to disentangle the physics of the manipulated excitations from that of the injection protocol. In particular, the spread-spectrum approach is shown to provide better knowledge of electronic Hong-Ou-Mandel correlations and to clarify the nature of the pulse train coherence and the role of the dynamical orthogonality catastrophe for noninteger charge injection.

  8. Optical potential study of electron scattering by rubidium

    Energy Technology Data Exchange (ETDEWEB)

    Chin, J. H.; Ratnavelu, K. [University of Malaya, Kuala Lumpur (Malaysia); Zhou, Y. [Harbin Institute of Technology, Harbin (China)

    2011-10-15

    The coupled-channel optical method (CCOM) has been implemented in a study of electronrubidium scattering. This method includes the continuum effect in the calculation via an ab-initio optical potential. Eight atomic states (5s, 5p, 4d, 6s, 6p, 5d, 7s, 7p) were used together with the continuum optical potential in the 5s-5s, 5s-5p, and 5p-5p coupling. The elastic, inelastic and total cross sections for electron-rubidium scattering at low and intermediate energies, ranging from 10 eV to 100 eV, are reported. The results are compared with available experimental and theoretical data.

  9. Characterization of polycapillary optics installed in an analytical electron microscope

    International Nuclear Information System (INIS)

    Takano, Akira; Maehata, Keisuke; Iyomoto, Naoko; Hara, Toru; Mitsuda, Kazuhisa; Yamasaki, Noriko; Tanaka, Keiichi

    2016-01-01

    An energy-dispersive spectrometer with a superconducting transition edge sensor (TES) microcalorimeter mounted on a scanning transmission electron microscope (STEM) is developed to enhance the accuracy of nanoscale materials analysis. TES microcalorimeters generally have sensitive surface areas of the order of 100 × 100 µm 2 . Also, the magnetic field generated by the STEM objective lens means that a TES microcalorimeter cannot be placed in a STEM column. We therefore use polycapillary optics to collect the X-rays. In this study, X-rays are collected from a STEM specimen and are then focused on a silicon drift detector; from these measurements, the optics are characterized and the experimental results are compared with the design of the optics. (author)

  10. Electronic structure and optical properties of AIN under high pressure

    International Nuclear Information System (INIS)

    Li Zetao; Dang Suihu; Li Chunxia

    2011-01-01

    We have calculated the electronic structure and optical properties of Wurtzite structure AIN under different high pressure with generalized gradient approximation (GGA) in this paper. The total energy, density of state, energy band structure and optical absorption and reflection properties under high pressure are calculated. By comparing the changes of the energy band structure, we obtained AIN phase transition pressure for 16.7 GPa, which is a direct band structure transforming to an indirect band structure. Meanwhile, according to the density of states distribution and energy band structure, we analyzed the optical properties of AIN under high-pressure, the results showed that the absorption spectra moved from low-energy to high-energy. (authors)

  11. Dephasing of optically generated electron spins in semiconductors

    International Nuclear Information System (INIS)

    Idrish Miah, M.

    2010-01-01

    Dephasing of optically generated electron spins in the presence of the external magnetic field and electric bias in semiconductor nano-structures has been studied by time- and polarization-resolved spectrometry. The obtained experimental data are presented in dependence of the strength of the magnetic field. The optically generated electron-spin precession frequency and dephasing time and rate are estimated. It is found that both the spin precession frequency and dephasing rate increase linearly with the external magnetic field up to about 9 T. However, the spin dephasing time is within sub-μs and is found to decrease exponentially with the strength of the external magnetic field. The results are discussed by exploring possible mechanisms of spin dephasing in low-dimensional semiconductor structures, where the quantum-confinement persists within the nano-range.

  12. Dephasing of optically generated electron spins in semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Idrish Miah, M., E-mail: m.miah@griffith.edu.a [Department of Physics, University of Chittagong, Chittagong, Chittagong - 4331 (Bangladesh)

    2010-09-13

    Dephasing of optically generated electron spins in the presence of the external magnetic field and electric bias in semiconductor nano-structures has been studied by time- and polarization-resolved spectrometry. The obtained experimental data are presented in dependence of the strength of the magnetic field. The optically generated electron-spin precession frequency and dephasing time and rate are estimated. It is found that both the spin precession frequency and dephasing rate increase linearly with the external magnetic field up to about 9 T. However, the spin dephasing time is within sub-{mu}s and is found to decrease exponentially with the strength of the external magnetic field. The results are discussed by exploring possible mechanisms of spin dephasing in low-dimensional semiconductor structures, where the quantum-confinement persists within the nano-range.

  13. Electronic structure and optical properties of metal doped tetraphenylporphyrins

    Science.gov (United States)

    Shah, Esha V.; Roy, Debesh R.

    2018-05-01

    A density functional scrutiny on the structure, electronic and optical properties of metal doped tetraphenylporphyrins MTPP (M=Fe, Co, Ni) is performed. The structural stability of the molecules is evaluated based on the electronic parameters like HOMO-LUMO gap (HLG), chemical hardness (η) and binding energy of the central metal atom to the molecular frame etc. The computed UltraViolet-Visible (UV-Vis) optical absorption spectra for all the compounds are also compared. The molecular structures reported are the lowest energy configurations. The entire calculations are carried out with a widely reliable functional, viz. B3LYP with a popular basis set which includes a scaler relativistic effect, viz. LANL2DZ.

  14. Organic structures design applications in optical and electronic devices

    CERN Document Server

    Chow, Tahsin J

    2014-01-01

    ""Presenting an overview of the syntheses and properties of organic molecules and their applications in optical and electronic devices, this book covers aspects concerning theoretical modeling for electron transfer, solution-processed micro- and nanomaterials, donor-acceptor cyclophanes, molecular motors, organogels, polyazaacenes, fluorogenic sensors based on calix[4]arenes, and organic light-emitting diodes. The publication of this book is timely because these topics have become very popular nowadays. The book is definitely an excellent reference for scientists working in these a

  15. Short wavelength optics for future free electron lasers

    International Nuclear Information System (INIS)

    Attwood, D.T.

    1984-04-01

    Although much free-electron laser work is directed toward achieving sufficient single-pass gain to be useful for research purposes, the availability of mirrors of high reflectance for the vacuum ultraviolet and soft x-ray regime would make resonant cavities a possibility. In addition, as in ordinary synchrotron radiation work, mirrors are required for the construction of realistic experiments and for beam manipulation purposes such as folding and extraction. The Working Group discussed a number of approaches to reflecting optics for free electron lasers, which are summarized here, and described in some detail. 16 references, 2 figures

  16. Surprise as a design strategy

    NARCIS (Netherlands)

    Ludden, G.D.S.; Schifferstein, H.N.J.; Hekkert, P.P.M.

    2008-01-01

    Imagine yourself queuing for the cashier’s desk in a supermarket. Naturally, you have picked the wrong line, the one that does not seem to move at all. Soon, you get tired of waiting. Now, how would you feel if the cashier suddenly started to sing? Many of us would be surprised and, regardless of

  17. OPTICAL-ELECTRONIC SYSTEM FOR EXPRESS ANALYSIS OF ORE DRESSABILITY FOR MINERAL RAW MATERIALS BY OPTICAL METHOD

    Directory of Open Access Journals (Sweden)

    A. A. Alekhin

    2013-05-01

    Full Text Available The article deals with creation results of experimental prototype of optical-electronic complex, designed to assess ore dressability of mineral raw materials by optical sorting method.

  18. Nanodiamond Landmarks for Subcellular Multimodal Optical and Electron Imaging

    Science.gov (United States)

    Zurbuchen, Mark A.; Lake, Michael P.; Kohan, Sirus A.; Leung, Belinda; Bouchard, Louis-S.

    2013-01-01

    There is a growing need for biolabels that can be used in both optical and electron microscopies, are non-cytotoxic, and do not photobleach. Such biolabels could enable targeted nanoscale imaging of sub-cellular structures, and help to establish correlations between conjugation-delivered biomolecules and function. Here we demonstrate a sub-cellular multi-modal imaging methodology that enables localization of inert particulate probes, consisting of nanodiamonds having fluorescent nitrogen-vacancy centers. These are functionalized to target specific structures, and are observable by both optical and electron microscopies. Nanodiamonds targeted to the nuclear pore complex are rapidly localized in electron-microscopy diffraction mode to enable “zooming-in” to regions of interest for detailed structural investigations. Optical microscopies reveal nanodiamonds for in-vitro tracking or uptake-confirmation. The approach is general, works down to the single nanodiamond level, and can leverage the unique capabilities of nanodiamonds, such as biocompatibility, sensitive magnetometry, and gene and drug delivery. PMID:24036840

  19. Irradiation Effects of Electron Beam on Optical Fibers

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Kyu; Cho, Gyu Seong [KAIST, Daejeon (Korea, Republic of); Choi, Hong Gu; Oh, Kyung Hwan [Yonsei University, Seoul (Korea, Republic of); Cho, Ho Jin [Nucron Co. Ltd., Seoul (Korea, Republic of)

    2009-10-15

    The surveillance or monitoring systems used in space station, nuclear power plant and nuclear waste repository, are often equipped with optical fibers to remotely locating expensive camera systems so as to protect them from direct irradiation. Especially in nuclear power plant and nuclear waste repository, irradiation by gamma-ray and beta-ray are most concerned. The effective life-time of such surveillance system may depend on the soundness of the optical fiber because it is the component to be exposed the high intensity of radiation field by purpose. Though the degradation of mechanical properties such as hardness and elasticity may occur but the degradation of the optical property such as spectral transmittance is the most possible cause of the effective life-time limitation. Generally 30 % reduction of light signal transmittance is considered as the life-time threshold point of such optical systems. In this paper, we studied irradiation effects on spectral transparency of various commonly-used optical fibers with high energy electron beam to conveniently simulate the both gamma-ray and beta-ray irradiation situation.

  20. Simulation of Non-Uniform Electron Beams in the Gyrotron Electron-Optical System

    Science.gov (United States)

    Louksha, O. I.; Trofimov, P. A.

    2018-04-01

    New calculated data on the effect of emission inhomogeneities on the quality of the electron beam, which is formed in an electron-optical system of a gyrotron, have been obtained. The calculations were based on emission current density distributions, which were measured for the different cathodes in the gyrotron of Peter the Great St. Petersburg Polytechnic University. A satisfactory agreement between the experimental and calculated data on the influence of emission nonuniformities on the velocity spread of electrons has been shown. The necessity of considering the real distribution of the emission current density over the cathode surface to determine the main parameters of the electron beam—the velocity and energy spreads of the electrons, spatial structure of the beam, and coefficient of reflection of electrons from the magnetic mirror—has been demonstrated. The maximum level of emission inhomogeneities, which are permissible for effective work of gyrotrons, has been discussed.

  1. Applied Electronics and Optical Laboratory: an optimized practical course for comprehensive training on optics and electronics

    Science.gov (United States)

    Wang, Kaiwei; Wang, Xiaoping

    2017-08-01

    In order to enhance the practical education and hands-on experience of optoelectronics and eliminate the overlapping contents that previously existed in the experiments section adhering to several different courses, a lab course of "Applied Optoelectronics Laboratory" has been established in the College of Optical Science and Engineering, Zhejiang University. The course consists of two sections, i.e., basic experiments and project design. In section 1, basic experiments provide hands-on experience with most of the fundamental concept taught in the corresponding courses. These basic experiments including the study of common light sources such as He-Ne laser, semiconductor laser and solid laser and LED; the testing and analysis of optical detectors based on effects of photovoltaic effect, photoconduction effect, photo emissive effect and array detectors. In section 2, the course encourages students to build a team and establish a stand-alone optical system to realize specific function by taking advantage of the basic knowledge learned from section 1. Through these measures, students acquired both basic knowledge and the practical application skills. Moreover, interest in science has been developed among students.

  2. Electron spin control of optically levitated nanodiamonds in vacuum.

    Science.gov (United States)

    Hoang, Thai M; Ahn, Jonghoon; Bang, Jaehoon; Li, Tongcang

    2016-07-19

    Electron spins of diamond nitrogen-vacancy (NV) centres are important quantum resources for nanoscale sensing and quantum information. Combining NV spins with levitated optomechanical resonators will provide a hybrid quantum system for novel applications. Here we optically levitate a nanodiamond and demonstrate electron spin control of its built-in NV centres in low vacuum. We observe that the strength of electron spin resonance (ESR) is enhanced when the air pressure is reduced. To better understand this system, we investigate the effects of trap power and measure the absolute internal temperature of levitated nanodiamonds with ESR after calibration of the strain effect. We also observe that oxygen and helium gases have different effects on both the photoluminescence and the ESR contrast of nanodiamond NV centres, indicating potential applications of NV centres in oxygen gas sensing. Our results pave the way towards a levitated spin-optomechanical system for studying macroscopic quantum mechanics.

  3. Electron spin control of optically levitated nanodiamonds in vacuum

    Science.gov (United States)

    Hoang, Thai M.; Ahn, Jonghoon; Bang, Jaehoon; Li, Tongcang

    2016-07-01

    Electron spins of diamond nitrogen-vacancy (NV) centres are important quantum resources for nanoscale sensing and quantum information. Combining NV spins with levitated optomechanical resonators will provide a hybrid quantum system for novel applications. Here we optically levitate a nanodiamond and demonstrate electron spin control of its built-in NV centres in low vacuum. We observe that the strength of electron spin resonance (ESR) is enhanced when the air pressure is reduced. To better understand this system, we investigate the effects of trap power and measure the absolute internal temperature of levitated nanodiamonds with ESR after calibration of the strain effect. We also observe that oxygen and helium gases have different effects on both the photoluminescence and the ESR contrast of nanodiamond NV centres, indicating potential applications of NV centres in oxygen gas sensing. Our results pave the way towards a levitated spin-optomechanical system for studying macroscopic quantum mechanics.

  4. Electron localization and optical absorption of polygonal quantum rings

    Science.gov (United States)

    Sitek, Anna; Serra, Llorenç; Gudmundsson, Vidar; Manolescu, Andrei

    2015-06-01

    We investigate theoretically polygonal quantum rings and focus mostly on the triangular geometry where the corner effects are maximal. Such rings can be seen as short core-shell nanowires, a generation of semiconductor heterostructures with multiple applications. We show how the geometry of the sample determines the electronic energy spectrum, and also the localization of electrons, with effects on the optical absorption. In particular, we show that irrespective of the ring shape low-energy electrons are always attracted by corners and are localized in their vicinity. The absorption spectrum in the presence of a magnetic field shows only two peaks within the corner-localized state domain, each associated with different circular polarization. This picture may be changed by an external electric field which allows previously forbidden transitions, and thus enables the number of corners to be determined. We show that polygonal quantum rings allow absorption of waves from distant ranges of the electromagnetic spectrum within one sample.

  5. Electron Spin Optical Orientation in Charged Quantum Dots

    Science.gov (United States)

    Shabaev, A.; Gershoni, D.; Korenev, V. L.

    2005-03-01

    We present a theory of nonresonant optical orientation of electron spins localized in quantum dots. This theory explains the negative circularly polarized photoluminescence of singlet trions localized in quantum dots previously observed in experiments where trion polarization changed to negative with time and where the degree of the negative polarization increased with intensity of pumping light. We have shown that this effect can be explained by the accumulation of dark excitons that occurs due to the spin blocking of the singlet trion formation - the major mechanism of dark exciton recombination. The accumulation of dark excitons results from a lack of electrons with a spin matching the exciton polarization. The electron spin lifetime is shortened by a transverse magnetic field or a temperature increase. This takes the block off the dark exciton recombination and restores the positive degree of trion polarization. The presented theory gives good agreement with experimental data.

  6. Electronic and optical properties of diamond/organic semiconductor heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Gajewski, Wojciech; Garrido, Jose; Niedermeier, Martin; Stutzmann, Martin [Walter Schottky Institute, TU Muenchen, Am Coulombwall 3, 85748 Garching (Germany); Williams, Oliver; Haenen, Ken [Institute for Materials Research, University of Hasselt, Wetenschapspark 1, BE-3590 Diepenbeek (Belgium)

    2007-07-01

    Different diamond substrates (single crystalline: SCD, poly-crystalline: PCD and nano-crystalline: NCD) were used to investigate the electronic and optical properties of the diamond/organic semiconductor heterostructures. Layers of a poly[ethynyl-(2-decyloxy-5methoxy)benzene] - PEB, pentacene and 4-nitro-biphenyl-4-diazonium cations - Ph-Ph-NO{sub 2} were prepared by spin coating, thermal evaporation and grafting, respectively. The measurements of the electronic transport along the organic layer were performed using a Hg probe as well as Hall effect measurements in the temperature range 70-400 K. The I-V characteristics of the B-doped diamond/organic semiconductor heterostructures were measured at room temperature by means of the Hg probe. Undoped IIa and undoped PCD films were used for a study of the optical and optoelectronic properties of prepared heterostructures. The influence of the organic layer homogeneity and layer thickness on the optical properties will be discussed. Furthermore, preliminary data on perpendicular and parallel transport in the heterostructures layer will be reported.

  7. Electronic and Optical Properties of Twisted Bilayer Graphene

    Science.gov (United States)

    Huang, Shengqiang

    The ability to isolate single atomic layers of van der Waals materials has led to renewed interest in the electronic and optical properties of these materials as they can be fundamentally different at the monolayer limit. Moreover, these 2D crystals can be assembled together layer by layer, with controllable sequence and orientation, to form artificial materials that exhibit new features that are not found in monolayers nor bulk. Twisted bilayer graphene is one such prototype system formed by two monolayer graphene layers placed on top of each other with a twist angle between their lattices, whose electronic band structure depends on the twist angle. This thesis presents the efforts to explore the electronic and optical properties of twisted bilayer graphene by Raman spectroscopy and scanning tunneling microscopy measurements. We first synthesize twisted bilayer graphene with various twist angles via chemical vapor deposition. Using a combination of scanning tunneling microscopy and Raman spectroscopy, the twist angles are determined. The strength of the Raman G peak is sensitive to the electronic band structure of twisted bilayer graphene and therefore we use this peak to monitor changes upon doping. Our results demonstrate the ability to modify the electronic and optical properties of twisted bilayer graphene with doping. We also fabricate twisted bilayer graphene by controllable stacking of two graphene monolayers with a dry transfer technique. For twist angles smaller than one degree, many body interactions play an important role. It requires eight electrons per moire unit cell to fill up each band instead of four electrons in the case of a larger twist angle. For twist angles smaller than 0.4 degree, a network of domain walls separating AB and BA stacking regions forms, which are predicted to host topologically protected helical states. Using scanning tunneling microscopy and spectroscopy, these states are confirmed to appear on the domain walls when inversion

  8. Extending electro-optic detection to ultrashort electron beams

    Directory of Open Access Journals (Sweden)

    M. H. Helle

    2012-05-01

    Full Text Available We propose a technique to extend noninvasive electro-optic detection of relativistic electron beams to bunch lengths of ≃10  fs. This is made possible by detecting the frequency mixing that occurs between the optical probe and the space charge fields of the beam, while simultaneously time resolving the resulting mixed frequency signal. The necessary formalism to describe this technique is developed and numerical solutions for various possible experimental conditions are made. These solutions are then compared to simulation results for consistency. Finally, the method to reconstruct the original bunch profile from the proposed diagnostic is discussed and an example showing a 15 fs test beam reconstructed to within an accuracy of 15% is given.

  9. Optically transparent semiconducting polymer nanonetwork for flexible and transparent electronics

    Science.gov (United States)

    Yu, Kilho; Park, Byoungwook; Kim, Geunjin; Kim, Chang-Hyun; Park, Sungjun; Kim, Jehan; Jung, Suhyun; Jeong, Soyeong; Kwon, Sooncheol; Kang, Hongkyu; Kim, Junghwan; Yoon, Myung-Han; Lee, Kwanghee

    2016-01-01

    Simultaneously achieving high optical transparency and excellent charge mobility in semiconducting polymers has presented a challenge for the application of these materials in future “flexible” and “transparent” electronics (FTEs). Here, by blending only a small amount (∼15 wt %) of a diketopyrrolopyrrole-based semiconducting polymer (DPP2T) into an inert polystyrene (PS) matrix, we introduce a polymer blend system that demonstrates both high field-effect transistor (FET) mobility and excellent optical transparency that approaches 100%. We discover that in a PS matrix, DPP2T forms a web-like, continuously connected nanonetwork that spreads throughout the thin film and provides highly efficient 2D charge pathways through extended intrachain conjugation. The remarkable physical properties achieved using our approach enable us to develop prototype high-performance FTE devices, including colorless all-polymer FET arrays and fully transparent FET-integrated polymer light-emitting diodes. PMID:27911774

  10. Optical rotation and electron spin resonance of an electro-optically active polythiophene

    International Nuclear Information System (INIS)

    Goto, Hiromasa

    2010-01-01

    Graphical abstract: The electro-chiroptical polythiophene displays optical rotation at wavelengths corresponding to the doping band observable in the absorption spectra. The formation of polarons on the main-chain is confirmed by electron spin resonance measurements. - Abstract: A chiroptical polythiophene, is synthesized by electrolytic polymerization in a cholesteric liquid crystal electrolyte solution. The polymer displays a fingerprint texture similar to that of the cholesteric electrolyte solution. Upon electrochemical doping, the polymer displays optical rotation at wavelengths corresponding to the doping band observable in the absorption spectra. The formation of polarons on the main-chain is confirmed by electron spin resonance measurements. The results demonstrate the intermolecular chirality of polarons in this π-conjugated polymer, indicating continuum delocalized polarons are in a three-dimensional helical environment.

  11. Structural, electronic and optical properties of carbon nitride

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, M L [California Univ., Berkeley (United States). Dept. of Physics

    1996-05-01

    Carbon nitride was proposed as a superhard material and a structural prototype, {beta}-C{sub 3}N{sub 4}, was examined using several theoretical models. Some reports claiming experimental verifications have been made recently. The current status of the theory and experiment is reviewed, and a detailed discussion is presented of calculations of the electronic and optical properties of this material. These calculations predict that {beta}-C{sub 3}N{sub 4} will have a minimum gap which is indirect at 6.4{+-}0.5 eV. A discussion of the possibility of carbon nitride nanotubes is also presented. (orig.)

  12. Optical conductivity and electronic Raman response of cuprate superconductors

    International Nuclear Information System (INIS)

    Vanyolos, A.; Dora, B.; Virosztek, A.

    2010-01-01

    We present the results of detailed analytical calculations for the in-plane optical conductivity and the electronic Raman susceptibility in quasi two-dimensional systems possessing a ground state with two competing order parameters: a d-wave density wave (dDW) and d-wave superconductor (dSC). In the coexisting dDW+dSC phase we determine the frequency dependence of these correlation functions in the presence of randomly distributed non-magnetic impurities in the unitary limit.

  13. Quantum theory of the optical and electronic properties of semiconductors

    CERN Document Server

    Haug, Hartmut

    1990-01-01

    The current technological revolution in the development of computing devices has created a demand for a textbook on the quantum theory of the electronic and optical properties of semiconductors and semiconductor devices. This book successfully fulfills this need. Based on lectures given by the authors, it is a comprehensive introduction for researchers or graduate-level students to the subject. Certain sections can also serve as a graduate-level textbook for use in solid state physics courses or for more specialized courses. The final chapters establish a direct link to current research in sem

  14. Optical beam diagnostics at the Electron Stretcher Accelerator ELSA

    International Nuclear Information System (INIS)

    Zander, Sven

    2013-10-01

    At the ELectron Stretcher Accelerator ELSA, a resonant excitation of the horizontal particle oscillations is used to extract the electrons to the experiments. This so-called resonance extraction influences the properties of the extracted beam. The emittance, as a number of the beam quality, was determined by using synchrotron light monitors. To enable broad investigations of the emittance a system of synchrotron light monitors was set up. This system was used to measure the influence of the extraction method on the emittance. Time resolved measurements were conducted to investigate the development of the emittance during an accelerator cycle. To improve the optical beam diagnostics a new beamline to an external laboratory was constructed. There, a new high resolution synchrotron light monitor was commissioned. In addition, a streak camera has been installed to enable longitudinal diagnostics of the beam profiles. First measurements of the longitudinal charge distribution with a time resolution in the range of a few picoseconds were conducted successfully.

  15. Correlative Stochastic Optical Reconstruction Microscopy and Electron Microscopy

    Science.gov (United States)

    Kim, Doory; Deerinck, Thomas J.; Sigal, Yaron M.; Babcock, Hazen P.; Ellisman, Mark H.; Zhuang, Xiaowei

    2015-01-01

    Correlative fluorescence light microscopy and electron microscopy allows the imaging of spatial distributions of specific biomolecules in the context of cellular ultrastructure. Recent development of super-resolution fluorescence microscopy allows the location of molecules to be determined with nanometer-scale spatial resolution. However, correlative super-resolution fluorescence microscopy and electron microscopy (EM) still remains challenging because the optimal specimen preparation and imaging conditions for super-resolution fluorescence microscopy and EM are often not compatible. Here, we have developed several experiment protocols for correlative stochastic optical reconstruction microscopy (STORM) and EM methods, both for un-embedded samples by applying EM-specific sample preparations after STORM imaging and for embedded and sectioned samples by optimizing the fluorescence under EM fixation, staining and embedding conditions. We demonstrated these methods using a variety of cellular targets. PMID:25874453

  16. Precision laser processing for micro electronics and fiber optic manufacturing

    Science.gov (United States)

    Webb, Andrew; Osborne, Mike; Foster-Turner, Gideon; Dinkel, Duane W.

    2008-02-01

    The application of laser based materials processing for precision micro scale manufacturing in the electronics and fiber optic industry is becoming increasingly widespread and accepted. This presentation will review latest laser technologies available and discuss the issues to be considered in choosing the most appropriate laser and processing parameters. High repetition rate, short duration pulsed lasers have improved rapidly in recent years in terms of both performance and reliability enabling flexible, cost effective processing of many material types including metal, silicon, plastic, ceramic and glass. Demonstrating the relevance of laser micromachining, application examples where laser processing is in use for production will be presented, including miniaturization of surface mount capacitors by applying a laser technique for demetalization of tracks in the capacitor manufacturing process and high quality laser machining of fiber optics including stripping, cleaving and lensing, resulting in optical quality finishes without the need for traditional polishing. Applications include telecoms, biomedical and sensing. OpTek Systems was formed in 2000 and provide fully integrated systems and sub contract services for laser processes. They are headquartered in the UK and are establishing a presence in North America through a laser processing facility in South Carolina and sales office in the North East.

  17. Implementation of Optical Characterization for Flexible Organic Electronics Applications

    Science.gov (United States)

    Laskarakis, A.; Logothetidis, S.

    One of the most rapidly evolving sectors of the modern science and technology is the flexible organic electronic devices (FEDs) that are expected to significantly improve and revolutionize our everyday life. The FED application includes the generation of electricity by renewable sources (by organic photovoltaic cells - OPVs), power storage (thin film batteries), the visualization of information (by organic displays), the working and living environment (ambient lighting, sensors), safety, market (smart labels, radio frequency identification tags - RFID), textiles (smart fabrics with embedded display and sensor capabilities), as well as healthcare (smart sensors for vital sign monitoring), etc. Although there has been important progresses in inorganic-based Si devices, there are numerous advances in the organic (semiconducting, conducting), inorganic, and hybrid (organic-inorganic) materials that exhibit desirable properties and stability, and in the synthesis and preparation methods. The understanding of the organic material properties can lead to the fast progress of the functionality and performance of FEDs. The investigation of the optical properties of these materials can promote the understanding of the optical, electrical, structural properties of organic semiconductors and electrodes and can contribute to the optimization of the synthesis process and the tuning of their structure and morphology. In this chapter, we will describe briefly some of the advances toward the implementation of optical characterization methods, such as Spectroscopic Ellipsometry (SE) from the infrared to the visible and ultraviolet spectral region for the study of materials (flexible polymer substrates, barrier layers, transparent electrodes) to be used for application in the fabrication of FEDs.

  18. Modeling a Miniaturized Scanning Electron Microscope Focusing Column - Lessons Learned in Electron Optics Simulation

    Science.gov (United States)

    Loyd, Jody; Gregory, Don; Gaskin, Jessica

    2016-01-01

    This presentation discusses work done to assess the design of a focusing column in a miniaturized Scanning Electron Microscope (SEM) developed at the NASA Marshall Space Flight Center (MSFC) for use in-situ on the Moon-in particular for mineralogical analysis. The MSFC beam column design uses purely electrostatic fields for focusing, because of the severe constraints on mass and electrical power consumption imposed by the goals of lunar exploration and of spaceflight in general. The resolution of an SEM ultimately depends on the size of the focused spot of the scanning beam probe, for which the stated goal here is a diameter of 10 nanometers. Optical aberrations are the main challenge to this performance goal, because they blur the ideal geometrical optical image of the electron source, effectively widening the ideal spot size of the beam probe. In the present work the optical aberrations of the mini SEM focusing column were assessed using direct tracing of non-paraxial rays, as opposed to mathematical estimates of aberrations based on paraxial ray-traces. The geometrical ray-tracing employed here is completely analogous to ray-tracing as conventionally understood in the realm of photon optics, with the major difference being that in electron optics the lens is simply a smoothly varying electric field in vacuum, formed by precisely machined electrodes. Ray-tracing in this context, therefore, relies upon a model of the electrostatic field inside the focusing column to provide the mathematical description of the "lens" being traced. This work relied fundamentally on the boundary element method (BEM) for this electric field model. In carrying out this research the authors discovered that higher accuracy in the field model was essential if aberrations were to be reliably assessed using direct ray-tracing. This led to some work in testing alternative techniques for modeling the electrostatic field. Ultimately, the necessary accuracy was attained using a BEM

  19. Electronic, structural, and optical properties of crystalline yttria

    International Nuclear Information System (INIS)

    Xu, Y.; Gu, Z.; Ching, W.Y.

    1997-01-01

    The electronic structure of crystalline Y 2 O 3 is investigated by first-principles calculations within the local-density approximation (LDA) of the density-functional theory. Results are presented for the band structure, the total density of states (DOS), the atom- and orbital-resolved partial DOS, effective charges, bond order, and charge-density distributions. Partial covalent character in the Y-O bonding is shown, and the nonequivalency of the two Y sites is demonstrated. The calculated electronic structure is compared with a variety of available experimental data. The total energy of the crystal is calculated as a function of crystal volume. A bulk modulus B of 183 Gpa and a pressure coefficient B ' of 4.01 are obtained, which are in good agreement with compression data. An LDA band gap of 4.54 eV at Γ is obtained which increases with pressure at a rate of dE g /dP=0.012eV/Gpa at the equilibrium volume. Also investigated are the optical properties of Y 2 O 3 up to a photon energy of 20 eV. The calculated complex dielectric function and electron-energy-loss function are in good agreement with experimental data. A static dielectric constant of var-epsilon(0)=3.20 is obtained. It is also found that the bottom of the conduction band consists of a single band, and direct optical transition at Γ between the top of the valence band and the bottom of the conduction band may be symmetry forbidden. copyright 1997 The American Physical Society

  20. Modifying the electronic and optical properties of carbon nanotubes

    Science.gov (United States)

    Kinder, Jesse M.

    The intrinsic electronic and optical properties of carbon nanotubes make them promising candidates for circuit elements and LEDs in nanoscale devices. However, applied fields and interactions with the environment can modify these intrinsic properties. This dissertation is a theoretical study of perturbations to an ideal carbon nanotube. It illustrates how transport and optical properties of carbon nanotubes can be adversely affected or intentionally modified by the local environment. The dissertation is divided into three parts. Part I analyzes the effect of a transverse electric field on the single-electron energy spectrum of semiconducting carbon nanotubes. Part II analyzes the effect of the local environment on selection rules and decay pathways relevant to dark excitons. Part III is a series of 26 appendices. Two different models for a transverse electric field are introduced in Part I. The first is a uniform field perpendicular to the nanotube axis. This model suggests the field has little effect on the band gap until it exceeds a critical value that can be tuned with strain or a magnetic field. The second model is a transverse field localized to a small region along the nanotube axis. The field creates a pair of exponentially localized bound states but has no effect on the band gap for particle transport. Part II explores the physics of dark excitons in carbon nanotubes. Two model calculations illustrate the effect of the local environment on allowed optical transitions and nonradiative recombination pathways. The first model illustrates the role of inversion symmetry in the optical spectrum. Broken inversion symmetry may explain low-lying peaks in the exciton spectrum of boron nitride nanotubes and localized photoemission around impurities and interfaces in carbon nanotubes. The second model in Part II suggests that free charge carriers can mediate an efficient nonradiative decay process for dark excitons in carbon nanotubes. The appendices in Part III

  1. Optical and electronic properties of polyvinyl alcohol doped with pairs of mixed valence metal ions

    International Nuclear Information System (INIS)

    Bulinski, Mircea; Kuncser, Victor; Plapcianu, Carmen; Krautwald, Stefan; Franke, Hilmar; Rotaru, P; Filoti, George

    2004-01-01

    The electronic mechanisms induced by the UV exposure of thin films of polyvinyl alcohol doped with pairs of mixed valence metal ions were studied in relation to their optical behaviour by Moessbauer spectroscopy and optical absorption. The results obtained definitely point to the role of each element from the pair in the electronic mechanism involved, with influence on the optical properties regarding applications in real-time holography and integrated optics

  2. Transmission electron microscope sample holder with optical features

    Science.gov (United States)

    Milas, Mirko [Port Jefferson, NY; Zhu, Yimei [Stony Brook, NY; Rameau, Jonathan David [Coram, NY

    2012-03-27

    A sample holder for holding a sample to be observed for research purposes, particularly in a transmission electron microscope (TEM), generally includes an external alignment part for directing a light beam in a predetermined beam direction, a sample holder body in optical communication with the external alignment part and a sample support member disposed at a distal end of the sample holder body opposite the external alignment part for holding a sample to be analyzed. The sample holder body defines an internal conduit for the light beam and the sample support member includes a light beam positioner for directing the light beam between the sample holder body and the sample held by the sample support member.

  3. Simulation of electron beam formation and transport in a gas-filled electron-optical system with a plasma emitter

    Energy Technology Data Exchange (ETDEWEB)

    Grishkov, A. A. [Russian Academy of Sciences, Institute of High Current Electronics, Siberian Branch (Russian Federation); Kornilov, S. Yu., E-mail: kornilovsy@gmail.com; Rempe, N. G. [Tomsk State University of Control Systems and Radioelectronics (Russian Federation); Shidlovskiy, S. V. [Tomsk State University (Russian Federation); Shklyaev, V. A. [Russian Academy of Sciences, Institute of High Current Electronics, Siberian Branch (Russian Federation)

    2016-07-15

    The results of computer simulations of the electron-optical system of an electron gun with a plasma emitter are presented. The simulations are performed using the KOBRA3-INP, XOOPIC, and ANSYS codes. The results describe the electron beam formation and transport. The electron trajectories are analyzed. The mechanisms of gas influence on the energy inhomogeneity of the beam and its current in the regions of beam primary formation, acceleration, and transport are described. Recommendations for optimizing the electron-optical system with a plasma emitter are presented.

  4. Geometry, electronic structures and optical properties of phosphorus nanotubes

    International Nuclear Information System (INIS)

    Hu, Tao; Hashmi, Arqum; Hong, Jisang

    2015-01-01

    Using a first principles approach, we investigated the geometry, electronic structures, and optical properties of phosphorus nanotubes (PNTs). Two possible 1D configurations, the so-called α-PNTs and β-PNTs, are proposed, which are structurally related to blue and black phosphorus monolayers, respectively. Hereby, we predict that both armchair and zigzag geometries can be synthesized in α-PNTs, but the zigzag form of β-PNT is highly unfavorable because of large strain and conformation energies. The band gap of α-PNTs is expected to be ∼2.67 eV, and this is insensitive to the chirality when the tube’s inner diameter is larger than 1.3 nm, while the armchair β-PNTs have a much smaller band gap. Interestingly, we find nearly flat band structures in the zigzag α-PNT system. This may indicate that an excited particle–hole pair has a huge effective mass. We also find asymmetric optical properties with respect to the polarization direction. The armchair α-PNT for parallel polarization shows a large refractive index of 2.6 near the ultraviolet wavelength, and also we find that the refractive index can be even smaller than 1 in certain frequency ranges. The zigzag tubes show very weak reflectivity for parallel polarization, while the armchair tube displays high reflectivity. (paper)

  5. Optical properties of electron-irradiated gallium phosphide

    International Nuclear Information System (INIS)

    Brailovskii, E.Yu.; Grigoryan, N.E.; Eritsyan, G.N.

    1980-01-01

    Results of optical absorption and photoconductivity measurements in the 0.1 to 2.4 eV range of GaP crystals irradiated with 7.5 and 50 MeV electrons are presented. The absorption of irradiated crystals near the edge can be represented by two exponential regions. In the free carrier absorption region one can observe as a result of irradiation a decrease of the power index p in the dependence α proportional to lambdap. Photoconductivity with long-time relaxation takes place in the spectral interval where the additional absorption is observed. The quenching of residual conductivity can be observed at hν=1.0eV. Variations in absorption and photoconductivity are attributed to the 'tails' of density states near the zone edges arising at introduction of both point defects and disordered regions. At hν=2.1eV one can observe a resonance band which is attributed to intra-centre transitions on point defects. A recovery of the optical properties of GaP at annealing is studied. In heavily irradiated GaP crystals point defects can form gatherings which display themselves as disordered regions. (author)

  6. Electronic, Optical, and Thermal Properties of Reduced-Dimensional Semiconductors

    Science.gov (United States)

    Huang, Shouting

    Reduced-dimensional materials have attracted tremendous attention because of their new physics and exotic properties, which are of great interests for fundamental science. More importantly, the manipulation and engineering of matter on an atomic scale yield promising applications for many fields including nanoelectronics, nanobiotechnology, environments, and renewable energy. Because of the unusual quantum confinement and enhanced surface effect of reduced-dimensional materials, traditional empirical models suffer from necessary but unreliable parameters extracted from previously-studied bulk materials. In this sense, quantitative, parameter-free approaches are highly useful for understanding properties of reduced-dimensional materials and, furthermore, predicting their novel applications. The first-principles density functional theory (DFT) is proven to be a reliable and convenient tool. In particular, recent progress in many-body perturbation theory (MBPT) makes it possible to calculate excited-state properties, e.g., quasiparticle (QP) band gap and optical excitations, by the first-principles approach based on DFT. Therefore, during my PhD study, I employed first-principles calculations based on DFT and MBPT to systematically study fundamental properties of typical reduced-dimensional semiconductors, i.e., the electronic structure, phonons, and optical excitations of core-shell nanowires (NWs) and graphene-like two-dimensional (2D) structures of current interests. First, I present first-principles studies on how to engineer band alignments of nano-sized radial heterojunctions, Si/Ge core-shell NWs. Our calculation reveals that band offsets in these one-dimensional (1D) nanostructures can be tailored by applying axial strain or varying core-shell sizes. In particular, the valence band offset can be efficiently tuned across a wide range and even be diminished via applied strain. Two mechanisms contribute to this tuning of band offsets. Furthermore, varying the

  7. Electronic and optical properties of Fe, Pd, and Ti studied by reflection electron energy loss spectroscopy

    International Nuclear Information System (INIS)

    Tahir, Dahlang; Kraaer, Jens; Tougaard, Sven

    2014-01-01

    We have studied the electronic and optical properties of Fe, Pd, and Ti by reflection electron energy-loss spectroscopy (REELS). REELS spectra recorded for primary energies in the range from 300 eV to 10 keV were corrected for multiple inelastically scattered electrons to determine the effective inelastic-scattering cross section. The dielectric functions and optical properties were determined by comparing the experimental inelastic-electron scattering cross section with a simulated cross section calculated within the semi-classical dielectric response model in which the only input is Im(−1/ε) by using the QUEELS-ε(k,ω)-REELS software package. The complex dielectric functions ε(k,ω), in the 0–100 eV energy range, for Fe, Pd, and Ti were determined from the derived Im(−1/ε) by Kramers-Kronig transformation and then the refractive index n and extinction coefficient k. The validity of the applied model was previously tested and found to give consistent results when applied to REELS spectra at energies between 300 and 1000 eV taken at widely different experimental geometries. In the present paper, we provide, for the first time, a further test on its validity and find that the model also gives consistent results when applied to REELS spectra in the full range of primary electron energies from 300 eV to 10000 eV. This gives confidence in the validity of the applied method.

  8. Optically stimulated luminescence in electronic components for emergency dosimetry

    International Nuclear Information System (INIS)

    Geber-Bergstrand, T.; Bernhardsson, C.; Mattsson, S.; Raeaef, C.L.

    2015-01-01

    Document available in abstract form only. Full text of publication follows: Accidents and, luckily more rarely, attacks involving nuclear or radiological material do occur from time to time. A very possible consequence of an accident or attack of this kind is that nearby people might be exposed to ionising radiation. Since these types of exposure situations, unlike the ones occurring in medicine, are unplanned, there are no radiation-monitoring data available. For several reasons, it is nevertheless of value to find out the dose that these people have received. The first and most urgent reason is after-the-event triage, to be able to carry out proper medical treatments and also to focus the available medical assets to the persons needing it the most. This is where different retrospective dosimetry techniques, such as luminescence, can be employed. Various electronic components from mobile phones and other portable devices have been studied using optically stimulated luminescence for their potential use in retrospective dosimetry. Previous investigations have been performed in laboratory conditions and have showed very promising properties for emergency dosimetry. In this study, the more practical parts of using electronic components in retrospective dosimetry have been considered. In a triage situation, one of the key parameters to consider is time; thus, effort has been made to speed up the readout procedure, yet without the loss of too much accuracy. (authors)

  9. Investigation of porous asphalt microstructure using optical and electron microscopy.

    Science.gov (United States)

    Poulikakos, L D; Partl, M N

    2010-11-01

    Direct observations of porous asphalt concrete samples in their natural state using optical and electron microscopy techniques led to useful information regarding the microstructure of two mixes and indicated a relationship between microstructure and in situ performance. This paper presents evidence that suboptimal microstructure can lead to premature failure thus making a first step in defining well or suboptimal performing pavements with a bottom-up approach (microstructure). Laboratory and field compaction produce different samples in terms of the microstructure. Laboratory compaction using the gyratory method has produced more microcracks in mineral aggregates after the binder had cooled. Well-performing mixes used polymer-modified binders, had a more homogeneous void structure with fewer elongated voids and better interlocking of the aggregates. Furthermore, well-performing mixes showed better distribution of the mastic and better coverage of the aggregates with bitumen. Low vacuum scanning electron microscopy showed that styrene butadiene styrene polymer modification in binder exists in the form of discontinuous globules and not continuous networks. A reduction in the polymer phase was observed as a result of aging and in-service use. © 2010 The Authors Journal compilation © 2010 The Royal Microscopical Society.

  10. Stable aqueous dispersions of optically and electronically active phosphorene.

    Science.gov (United States)

    Kang, Joohoon; Wells, Spencer A; Wood, Joshua D; Lee, Jae-Hyeok; Liu, Xiaolong; Ryder, Christopher R; Zhu, Jian; Guest, Jeffrey R; Husko, Chad A; Hersam, Mark C

    2016-10-18

    Understanding and exploiting the remarkable optical and electronic properties of phosphorene require mass production methods that avoid chemical degradation. Although solution-based strategies have been developed for scalable exfoliation of black phosphorus, these techniques have thus far used anhydrous organic solvents in an effort to minimize exposure to known oxidants, but at the cost of limited exfoliation yield and flake size distribution. Here, we present an alternative phosphorene production method based on surfactant-assisted exfoliation and postprocessing of black phosphorus in deoxygenated water. From comprehensive microscopic and spectroscopic analysis, this approach is shown to yield phosphorene dispersions that are stable, highly concentrated, and comparable to micromechanically exfoliated phosphorene in structure and chemistry. Due to the high exfoliation efficiency of this process, the resulting phosphorene flakes are thinner than anhydrous organic solvent dispersions, thus allowing the observation of layer-dependent photoluminescence down to the monolayer limit. Furthermore, to demonstrate preservation of electronic properties following solution processing, the aqueous-exfoliated phosphorene flakes are used in field-effect transistors with high drive currents and current modulation ratios. Overall, this method enables the isolation and mass production of few-layer phosphorene, which will accelerate ongoing efforts to realize a diverse range of phosphorene-based applications.

  11. Some Surprising Introductory Physics Facts and Numbers

    Science.gov (United States)

    Mallmann, A. James

    2016-01-01

    In the entertainment world, people usually like, and find memorable, novels, short stories, and movies with surprise endings. This suggests that classroom teachers might want to present to their students examples of surprising facts associated with principles of physics. Possible benefits of finding surprising facts about principles of physics are…

  12. Experimental results surprise quantum theory

    International Nuclear Information System (INIS)

    White, C.

    1986-01-01

    Interest in results from Darmstadt that positron-electron pairs are created in nuclei with high atomic numbers (in the Z range from 180-188) lies in the occurrence of a quantized positron kinetic energy peak at 300. The results lend substance to the contention of Erich Bagge that the traditionally accepted symmetries in positron-electron emission do not exist and, therefore, there is no need to posit the existence of the neutrino. The search is on for the decay of a previously unknown boson to account for the findings, which also points to the need for a major revision in quantum theory. 1 figure

  13. Shack-Hartmann Electron Densitometer (SHED): An Optical System for Diagnosing Free Electron Density in Laser-Produced Plasmas

    Science.gov (United States)

    2016-11-01

    Free Electron Density in Laser-Produced Plasmas by Anthony R Valenzuela Approved for public release; distribution is...AND SUBTITLE Shack-Hartmann Electron Densitometer (SHED): An Optical System for Diagnosing Free Electron Density in Laser-Produced Plasmas 5a...SUPPLEMENTARY NOTES 14. ABSTRACT The Shack-Hartmann Electron Densitometer is a novel method to diagnose ultrashort pulse laser–produced plasmas

  14. Study of the Welding Electron Gun Optical Properties for Work Piece Imaging

    Czech Academy of Sciences Publication Activity Database

    Vlček, Ivan

    2009-01-01

    Roč. 44, 5-6 (2009), s. 70-72 ISSN 0861-4717 R&D Projects: GA AV ČR KAN300100702 Institutional research plan: CEZ:AV0Z20650511 Keywords : electron beam welding * electron gun * electron optics design Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  15. Tuning of few-electron states and optical absorption anisotropy in GaAs quantum rings.

    Science.gov (United States)

    Wu, Zhenhua; Li, Jian; Li, Jun; Yin, Huaxiang; Liu, Yu

    2017-11-15

    The electronic and optical properties of a GaAs quantum ring (QR) with few electrons in the presence of the Rashba spin-orbit interaction (RSOI) and the Dresselhaus spin-orbit interaction (DSOI) have been investigated theoretically. The configuration interaction (CI) method is employed to calculate the eigenvalues and eigenstates of the multiple-electron QR accurately. Our numerical results demonstrate that the symmetry breaking induced by the RSOI and DSOI leads to an anisotropic distribution of multi-electron states. The Coulomb interaction offers additional modulation of the electron distribution and thus the optical absorption indices in the quantum rings. By tuning the magnetic/electric fields and/or electron numbers in a quantum ring, one can change its optical properties significantly. Our theory provides a new way to control the multi-electron states and optical properties of a QR by hybrid modulations or by electrical means only.

  16. Electronic Structure and Optical Properties Of EuIn2P2

    KAUST Repository

    Singh, Nirpendra

    2011-10-25

    The electronic structures and, optical and magneto‐optical properties of a newly found Zintl compound EuIn2P2 have been investigated within the density‐functional theory using the highly precise full‐potential linear‐augmented‐plane‐wave method. Results of detailed investigation of the electronic structure and related properties are reported.

  17. Equipment for evaluation of the characteristics of electronic-optic converters

    International Nuclear Information System (INIS)

    Getsov, Petar; Mardirossian, Garo; Nedkov, Rumen; Stoyanov, Stiliyan; Bo, Wang; Prokopenko, Olga; Boyanov, Petar

    2018-01-01

    In this paper we consider the concept, structure, operation and application of original equipment for evaluation of the characteristics of electronic-optic converters (EOC) created in the Space Research and Technologies Institute at the Bulgarian Academy of Sciences. The equipment is recognized as an invention and it is subject to patent protection. Key words: electronic-optic converter, infrared radiation, night surveillance devices

  18. U-10Mo Sample Preparation and Examination using Optical and Scanning Electron Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Prabhakaran, Ramprashad [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Joshi, Vineet V. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Rhodes, Mark A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Schemer-Kohrn, Alan L. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Guzman, Anthony D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lavender, Curt A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2016-10-01

    The purpose of this document is to provide guidelines to prepare specimens of uranium alloyed with 10 weight percent molybdenum (U-10Mo) for optical metallography and scanning electron microscopy. This document also provides instructions to set up an optical microscope and a scanning electron microscope to analyze U-10Mo specimens and to obtain the required information.

  19. U-10Mo Sample Preparation and Examination using Optical and Scanning Electron Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Prabhakaran, Ramprashad [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Joshi, Vineet V. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Rhodes, Mark A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Schemer-Kohrn, Alan L. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Guzman, Anthony D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lavender, Curt A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2016-03-30

    The purpose of this document is to provide guidelines to prepare specimens of uranium alloyed with 10 weight percent molybdenum (U-10Mo) for optical metallography and scanning electron microscopy. This document also provides instructions to set up an optical microscope and a scanning electron microscope to analyze U-10Mo specimens and to obtain the required information.

  20. Optical-phonon-induced frictional drag in coupled two-dimensional electron gases

    DEFF Research Database (Denmark)

    Hu, Ben Yu-Kuang

    1998-01-01

    The role of optical phonons in frictional drag between two adjacent but electrically isolated two-dimensional electron gases is investigated. Since the optical phonons in III-V materials have a considerably larger coupling to electrons than acoustic phonons (which are the dominant drag mechanism ...

  1. U-10Mo Sample Preparation and Examination using Optical and Scanning Electron Microscopy. Rev. 1

    International Nuclear Information System (INIS)

    Prabhakaran, Ramprashad; Joshi, Vineet V.; Rhodes, Mark A.; Schemer-Kohrn, Alan L.; Guzman, Anthony D.; Lavender, Curt A.

    2016-01-01

    The purpose of this document is to provide guidelines to prepare specimens of uranium alloyed with 10 weight percent molybdenum (U-10Mo) for optical metallography and scanning electron microscopy. This document also provides instructions to set up an optical microscope and a scanning electron microscope to analyze U-10Mo specimens and to obtain the required information.

  2. Average electronegativity, electronic polarizability and optical basicity of lanthanide oxides for different coordination numbers

    International Nuclear Information System (INIS)

    Zhao Xinyu; Wang Xiaoli; Lin Hai; Wang Zhiqiang

    2008-01-01

    On the basis of new electronegativity values, electronic polarizability and optical basicity of lanthanide oxides are calculated from the concept of average electronegativity given by Asokamani and Manjula. The estimated values are in close agreement with our previous conclusion. Particularly, we attempt to obtain new data of electronic polarizability and optical basicity of lanthanide sesquioxides for different coordination numbers (6-12). The present investigation suggests that both electronic polarizability and optical basicity increase gradually with increasing coordination number. We also looked for another double peak effect, that is, electronic polarizability and optical basicity of trivalent lanthanide oxides show a gradual decrease and then an abrupt increase at the Europia and Ytterbia. Furthermore, close correlations are investigated among average electronegativity, optical basicity, electronic polarizability and coordination number in this paper

  3. Advances in imaging and electron physics optics of charged particle analyzers

    CERN Document Server

    Hawkes, Peter W

    2011-01-01

    Advances in Imaging and Electron Physics merges two long-running serials--Advances in Electronics and Electron Physics and Advances in Optical and Electron Microscopy. This series features extended articles on the physics of electron devices (especially semiconductor devices), particle optics at high and low energies, microlithography, image science and digital image processing, electromagnetic wave propagation, electron microscopy, and the computing methods used in all these domains. Contributions from leading international scholars and industry experts Discusses hot topic areas and presents current and future research trends Invaluable reference and guide for physicists, engineers and mathematicians.

  4. Advances in imaging and electron physics optics of charged particle analyzers

    CERN Document Server

    Hawkes, Peter W

    2011-01-01

    Advances in Imaging and Electron Physics merges two long-running serials--Advances in Electronics and Electron Physics and Advances in Optical and Electron Microscopy. This series features extended articles on the physics of electron devices (especially semiconductor devices), particle optics at high and low energies, microlithography, image science and digital image processing, electromagnetic wave propagation, electron microscopy, and the computing methods used in all these domains. * Contributions from leading international scholars and industry experts * Discusses hot topic areas and presents current and future research trends * Invaluable reference and guide for physicists, engineers and mathematicians.

  5. Electron optics in hybrid photodetectors in magnetic fields

    International Nuclear Information System (INIS)

    Green, D.

    1996-12-01

    The CMS detector design has the hadronic calorimeter immersed in a 4 T magnetic field. The scintillator photon transducer must work reliably in this environment. The baseline phototransducer is the ''hybrid photomultiplier'', which consists of a standard photocathode (S20) followed by a high field acceleration onto the surface of a Si diode. Such a device has a linear response, 1 e out for every 3.6 eV of potential drop in excess of the threshold needed to penetrate the passivation layer of the diode. A threshold voltage of ∼2 kV is typical of these devices, leading to a gain of ∼2000 at 10 kV applied voltage. In the interest of reducing costs, the Si surface can be cut into pixels. However, the optics of the electron trajectories must be well understood so as to avoid crosstalk between pixels caused by misalignment of the accelerating electric field and the axis of the CMS magnetic field. The depletion depth of the Si is quite standard, ∼300 μm. The source capacity is ∼20 pF. The output pulse has a ∼6 nsec risetime for > 60 V diode biasing. The device is expected to be highly immune to magnetic field effects due to the short spacing, ∼3 mm, between photocathode and Si

  6. Optical and opto-electronic characterization of semiconducting nanostructures

    International Nuclear Information System (INIS)

    Offer, Matthias

    2011-01-01

    In the present thesis, the photoluminescence (PL) of cadmium selenide nanoparticles and doped gallium arsenide nanowires are investigated. Furthermore, in GaAs nanowires, with a distinct pn-junction in the direction of growth, electroluminescence (EL) is demonstrated and analyzed for the fist time. Using PL spectroscopy, the excitonic states of individual CdSe nanoparticles are studied. Sharp emission lines, which can be assigned to different excitonic transitions, can be observed. At a sample temperature of T≅10 K, line widths of ΔE FWHM ≤8 meV are found. Additionally, it is demonstrated that, apart from the main line, phonon replica of the LO and 2LO-phonon can be observed. An exciton in an ionized nanoparticle has the electronic structure of a trion. In silicon, the recombination of a trion in CdSe nanoparticles, while optically allowed, will not be detected visually because faster non-radiative Auger processes dominate (off-state). However, this work shows that, on a coated aluminium alloy substrate, the trions of single CdSe nanoparticles are observable. This observation is due to the reduction of the optical lifetime and is caused by surface plasmons. Instead of the commonly occurring off-state, a jump-like and discrete red shift of the emission energy of ΔE ∼24 meV is observed. This emission line can also be attributed to a negative trion. In addition, p- and n-doped GaAs nanowires are characterized using spatially resolved PL spectroscopy. The intrinsic stump of the nanowire shows the typical PL of GaAs. Through doping of the GaAs nanowire, there is a recognizable shift in the emission energy. This shift can be attributed to increasing dopant concentration. By analyzing the line shape, information regarding the distribution and concentration of the dopant can be found. Using these findings, the PL of a single GaAs nanowire with a distinct pn-junction in the direction of growth is examined. This observation shows that a compensated region develops

  7. Optical pumping of electron and nuclear spin in a negatively-charged quantum dot

    Science.gov (United States)

    Bracker, Allan; Gershoni, David; Korenev, Vladimir

    2005-03-01

    We report optical pumping of electron and nuclear spins in an individual negatively-charged quantum dot. With a bias-controlled heterostructure, we inject one electron into the quantum dot. Intense laser excitation produces negative photoluminescence polarization, which is easily erased by the Hanle effect, demonstrating optical pumping of a long-lived resident electron. The electron spin lifetime is consistent with the influence of nuclear spin fluctuations. Measuring the Overhauser effect in high magnetic fields, we observe a high degree of nuclear spin polarization, which is closely correlated to electron spin pumping.

  8. Optical and magneto-optical properties of the electron-doped and hole-doped C{sub 82} crystal

    Energy Technology Data Exchange (ETDEWEB)

    Rostampour, E., E-mail: el_rostampour@yahoo.com [Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Koohi, A. [Plasma Physics and Nuclear Fusion Research School, Nuclear Science and Technology Research Institute, AEOI, Tehran (Iran, Islamic Republic of)

    2015-01-15

    The optical and magnetic properties of the doped C{sub 82} crystal have been investigated by Su–Schrieffer–Heeger (SSH) model, which is based on the Ewald method. When the C{sub 82} molecule is doped with one electron (or hole), a single electron is remained in the energy level that affects the optical and magnetic properties of the C{sub 82} crystal. The lattice and electronic structures of C{sub 82} changed with doping electron (or hole) in the molecule of C{sub 82}. Therefore, polarons are predicted in doped fullerenes. The obtained results showed that the dielectric tensor of the C{sub 82} crystal increased with doping electron (or hole) in the molecule of C{sub 82}. The spectral shapes of the dielectric tensor, circular dichroism and birefringence coefficient of the C{sub 82} crystal turn out to be determined mainly by the geometrical distributions of the pentagons in the fullerene structures.

  9. New Electronic Technology Applied in Flexible Organic Optical System

    Directory of Open Access Journals (Sweden)

    Andre F. S. Guedes

    2014-02-01

    Full Text Available The synthesis and application of new organic materials, nanostructured, for developing technology based on organic devices, have been the main focus of the scientific community. In recent years, the first polymeric electronics products have entered the market (organic semiconductor materials and there are some electrochromic devices among them that have been called smart windows, once they control the passage of light or heat through a closed environment as an ordinary window. The main functional aspect of electrochromic devices, when being used in architectural and automotive industry, is to control the passage of light and temperature with thermal and visual comfort. These devices can be flexible and very thin, not containing heavy metals, and formed by layers of organic material deposited in several architectures. In this study, the electro-deposition of organic materials in the Polyaniline, PANI case, which provide stability in optical and electrical parameters, was utilized with the means of developing prototypes of organic electrochromic devices. These materials were characterized by: ultraviolet-visible spectroscopy absorption (UV-Vis, measurement of thickness (MT and electrical measurements (EM. This study aims to establish the relationship between the thickness of the active layer and the value of the electrical resistivity of the layer deposited through an electro-deposition technique. The experimental results enabled the equating of the electrical resistivity related to the thickness of the deposited layer. The linear fit of these results has expressed the thickness of the conducting layer, α, and the lowest value of the electrical resistivity, β, associated with the gap between the valence band and the conduction band. Thus, the results have demonstrated that, when the layer of organic material is completely conductive, we may obtain the thickness of the organic material deposited on the substrate.

  10. Optical sensor array platform based on polymer electronic devices

    Science.gov (United States)

    Koetse, Marc M.; Rensing, Peter A.; Sharpe, Ruben B. A.; van Heck, Gert T.; Allard, Bart A. M.; Meulendijks, Nicole N. M. M.; Kruijt, Peter G. M.; Tijdink, Marcel W. W. J.; De Zwart, René M.; Houben, René J.; Enting, Erik; van Veen, Sjaak J. J. F.; Schoo, Herman F. M.

    2007-10-01

    Monitoring of personal wellbeing and optimizing human performance are areas where sensors have only begun to be used. One of the reasons for this is the specific demands that these application areas put on the underlying technology and system properties. In many cases these sensors will be integrated in clothing, be worn on the skin, or may even be placed inside the body. This implies that flexibility and wearability of the systems is essential for their success. Devices based on polymer semiconductors allow for these demands since they can be fabricated with thin film technology. The use of thin film device technology allows for the fabrication of very thin sensors (e.g. integrated in food product packaging), flexible or bendable sensors in wearables, large area/distributed sensors, and intrinsically low-cost applications in disposable products. With thin film device technology a high level of integration can be achieved with parts that analyze signals, process and store data, and interact over a network. Integration of all these functions will inherently lead to better cost/performance ratios, especially if printing and other standard polymer technology such as high precision moulding is applied for the fabrication. In this paper we present an optical transmission sensor array based on polymer semiconductor devices made by thin film technology. The organic devices, light emitting diodes, photodiodes and selective medium chip, are integrated with classic electronic components. Together they form a versatile sensor platform that allows for the quantitative measurement of 100 channels and communicates wireless with a computer. The emphasis is given to the sensor principle, the design, fabrication technology and integration of the thin film devices.

  11. Quantum theory of the optical and electronic properties of semiconductors

    CERN Document Server

    Haug, Hartmut

    2009-01-01

    This invaluable textbook presents the basic elements needed to understand and research into semiconductor physics. It deals with elementary excitations in bulk and low-dimensional semiconductors, including quantum wells, quantum wires and quantum dots. The basic principles underlying optical nonlinearities are developed, including excitonic and many-body plasma effects. Fundamentals of optical bistability, semiconductor lasers, femtosecond excitation, the optical Stark effect, the semiconductor photon echo, magneto-optic effects, as well as bulk and quantum-confined Franz-Keldysh effects, are covered. The material is presented in sufficient detail for graduate students and researchers with a general background in quantum mechanics.This fifth edition includes an additional chapter on 'Quantum Optical Effects' where the theory of quantum optical effects in semiconductors is detailed. Besides deriving the 'semiconductor luminescence equations' and the expression for the stationary luminescence spectrum, the resu...

  12. Quantum coherent optical phase modulation in an ultrafast transmission electron microscope.

    Science.gov (United States)

    Feist, Armin; Echternkamp, Katharina E; Schauss, Jakob; Yalunin, Sergey V; Schäfer, Sascha; Ropers, Claus

    2015-05-14

    Coherent manipulation of quantum systems with light is expected to be a cornerstone of future information and communication technology, including quantum computation and cryptography. The transfer of an optical phase onto a quantum wavefunction is a defining aspect of coherent interactions and forms the basis of quantum state preparation, synchronization and metrology. Light-phase-modulated electron states near atoms and molecules are essential for the techniques of attosecond science, including the generation of extreme-ultraviolet pulses and orbital tomography. In contrast, the quantum-coherent phase-modulation of energetic free-electron beams has not been demonstrated, although it promises direct access to ultrafast imaging and spectroscopy with tailored electron pulses on the attosecond scale. Here we demonstrate the coherent quantum state manipulation of free-electron populations in an electron microscope beam. We employ the interaction of ultrashort electron pulses with optical near-fields to induce Rabi oscillations in the populations of electron momentum states, observed as a function of the optical driving field. Excellent agreement with the scaling of an equal-Rabi multilevel quantum ladder is obtained, representing the observation of a light-driven 'quantum walk' coherently reshaping electron density in momentum space. We note that, after the interaction, the optically generated superposition of momentum states evolves into a train of attosecond electron pulses. Our results reveal the potential of quantum control for the precision structuring of electron densities, with possible applications ranging from ultrafast electron spectroscopy and microscopy to accelerator science and free-electron lasers.

  13. The role of surprise in satisfaction judgements

    NARCIS (Netherlands)

    Vanhamme, J.; Snelders, H.M.J.J.

    2001-01-01

    Empirical findings suggest that surprise plays an important role in consumer satisfaction, but there is a lack of theory to explain why this is so. The present paper provides explanations for the process through which positive (negative) surprise might enhance (reduce) consumer satisfaction. First,

  14. Cathodoluminescence-activated nanoimaging: noninvasive near-field optical microscopy in an electron microscope.

    Science.gov (United States)

    Bischak, Connor G; Hetherington, Craig L; Wang, Zhe; Precht, Jake T; Kaz, David M; Schlom, Darrell G; Ginsberg, Naomi S

    2015-05-13

    We demonstrate a new nanoimaging platform in which optical excitations generated by a low-energy electron beam in an ultrathin scintillator are used as a noninvasive, near-field optical scanning probe of an underlying sample. We obtain optical images of Al nanostructures with 46 nm resolution and validate the noninvasiveness of this approach by imaging a conjugated polymer film otherwise incompatible with electron microscopy due to electron-induced damage. The high resolution, speed, and noninvasiveness of this "cathodoluminescence-activated" platform also show promise for super-resolution bioimaging.

  15. Ab initio calculation of the electronic and optical properties of solid pentacene

    International Nuclear Information System (INIS)

    Tiago, Murilo L.; Northrup, John E.; Louie, Steve G.

    2002-01-01

    The optical and electronic properties of crystalline pentacene are studied, using a first-principles Green's-function approach. The quasiparticle energies are calculated within the GW approximation and the electron-hole excitations are computed by solving the Bethe-Salpeter equation. We investigate the role of polymorphism on the electronic energy gap and linear optical spectrum by studying two different crystalline phases: the solution-phase structure and the vapor-phase structure. charge-transfer excitons are found to dominate the optical spectrum. Excitons with sizable binding energies are predicted for both phases

  16. Three-dimensional optical transfer functions in the aberration-corrected scanning transmission electron microscope.

    Science.gov (United States)

    Jones, L; Nellist, P D

    2014-05-01

    In the scanning transmission electron microscope, hardware aberration correctors can now correct for the positive spherical aberration of round electron lenses. These correctors make use of nonround optics such as hexapoles or octupoles, leading to the limiting aberrations often being of a nonround type. Here we explore the effect of a number of potential limiting aberrations on the imaging performance of the scanning transmission electron microscope through their resulting optical transfer functions. In particular, the response of the optical transfer function to changes in defocus are examined, given that this is the final aberration to be tuned just before image acquisition. The resulting three-dimensional optical transfer functions also allow an assessment of the performance of a system for focal-series experiments or optical sectioning applications. © 2014 The Authors Journal of Microscopy © 2014 Royal Microscopical Society.

  17. Energy modulation of nonrelativistic electrons in an optical near field on a metal microslit

    OpenAIRE

    R., Ishikawa; Jongsuck, Bae; K., Mizuno

    2001-01-01

    Energy modulation of nonrelativistic electrons with a laser beam using a metal microslit as an interaction circuit has been investigated. An optical near field is induced in the proximity of the microslit by illumination of the laser beam. The electrons passing close to the slit are accelerated or decelerated by an evanescent wave contained in the near field whose phase velocity is equal to the velocity of the electrons. The electron-evanescent wave interaction in the microslit has been analy...

  18. The optical design of 3D ICs for smartphone and optro-electronics sensing module

    Science.gov (United States)

    Huang, Jiun-Woei

    2018-03-01

    Smartphone require limit space for image system, current lens, used in smartphones are refractive type, the effective focal length is limited the thickness of phone physical size. Other, such as optro-electronics sensing chips, proximity optical sensors, and UV indexer chips are integrated into smart phone with limit space. Due to the requirement of multiple lens in smartphone, proximity optical sensors, UV indexer and other optro-electronics sensing chips in a limited space of CPU board in future smart phone, optro-electronics 3D IC's integrated with optical lens or components may be a key technology for 3 C products. A design for reflective lens is fitted to CMOS, proximity optical sensors, UV indexer and other optro-electronics sensing chips based on 3-D IC. The reflective lens can be threes times of effective focal lens, and be able to resolve small object. The system will be assembled and integrated in one 3-D IC more easily.

  19. Simulation of the behaviour of electron-optical systems using a parallel computer

    International Nuclear Information System (INIS)

    Balladore, J.L.; Hawkes, P.W.

    1990-01-01

    The advantage of using a multiprocessor computer for the calculation of electron-optical properties is investigated. A considerable reduction of computing time is obtained by reorganising the finite-element field computation. (orig.)

  20. Structural and optical properties of electron beam evaporated CdSe ...

    Indian Academy of Sciences (India)

    electronic applications such as photo detection or solar energy conversion, due to its optical and electrical properties, as well as its good chemical and mechanical stability. In order to explore the possibility of using this in optoelectronics, ...

  1. Optical model theory of elastic electron- and positron-atom scattering at intermediate energies

    International Nuclear Information System (INIS)

    Joachain, C.J.

    1977-01-01

    It is stated that the basic idea of the optical model theory is to enable analysis of the elastic scattering of a particle from a complex target by replacing the complicated interactions between the beam and the target by an optical potential, or pseudopotential, in which the incident particle moves. Once the optical potential is determined the original many-body elastic scattering problem reduces to a one-body situation. The resulting optical potential is, however, a very complicated operator, and the formal expressions obtained from first principles for the optical potential can only be evaluated approximately in a few simple cases, such as high energy elastic hadron-nucleus scattering, for the the optical potential can be expressed in terms of two-body hadron-nucleon amplitudes, and the non-relativistic elastic scattering of fast charged particles by atoms. The elastic scattering of an electron or positron by a neutral atom at intermediate energies is here considered. Exchange effects between the projectile and the atomic electrons are considered; also absorption and polarisation effects. Applications of the full-wave optical model have so far only been made to the elastic scattering of fast electrons and positrons by atomic H, He, Ne, and Ar. Agreements of the optical model results with absolute measurements of differential cross sections for electron scattering are very good, an agreement that improves as the energy increases, but deteriorates quickly as the incident energy becomes lower than 50 eV for atomic H or 100 eV for He. For more complex atoms the optical model calculations also appear very encouraging. With regard to positron-atom elastic scattering the optical model results for positron-He scattering differ markedly at small angles from the corresponding electron-He values. It would be interesting to have experimental angular distributions of positron-atom elastic scattering in order to check predictions of the optical model theory. (U.K.)

  2. Climate Change as a Predictable Surprise

    International Nuclear Information System (INIS)

    Bazerman, M.H.

    2006-01-01

    In this article, I analyze climate change as a 'predictable surprise', an event that leads an organization or nation to react with surprise, despite the fact that the information necessary to anticipate the event and its consequences was available (Bazerman and Watkins, 2004). I then assess the cognitive, organizational, and political reasons why society fails to implement wise strategies to prevent predictable surprises generally and climate change specifically. Finally, I conclude with an outline of a set of response strategies to overcome barriers to change

  3. Electronic band structure and optical properties of antimony selenide under pressure

    Energy Technology Data Exchange (ETDEWEB)

    Abhijit, B.K.; Jayaraman, Aditya; Molli, Muralikrishna, E-mail: muralikrishnamolli@sssihl.edu.in [Department of Physics, Sri Sathya Sai Institute of Higher Learning, Prasanthinilayam, 515 134 (India)

    2016-05-23

    In this work we present the optical properties of Antimony Selenide (Sb{sub 2}Se{sub 3}) under ambient conditions and under pressure of 9.2 GPa obtained using first principles calculations. We investigated the electronic band structure using the FP-LAPW method within the sphere of the density functional theory. Optical properties like refractive index, absorption coefficient and optical conductivity are calculated using the WIEN2k code.

  4. Electronic Structure and Optical Properties Of EuIn2P2

    KAUST Repository

    Singh, Nirpendra; Schwingenschlö gl, Udo; Rhee, J. Y.

    2011-01-01

    The electronic structures and, optical and magneto‐optical properties of a newly found Zintl compound EuIn2P2 have been investigated within the density‐functional theory using the highly precise full‐potential linear‐augmented‐plane‐wave method

  5. Optical properties, electronic structure and magnetism of alpha '-NaxV2O5

    NARCIS (Netherlands)

    Konstantinovic, MI; Popovic, ZV; Presura, C; Gajic, R; Isobe, M; Ueda, Y; Moshchalkov, VV

    2002-01-01

    The optical properties of sodium-deficient alpha'-NaxV2O5 (0.85 less than or equal to x less than or equal to 1.00) single crystals are analyzed using ellipsometry, and infrared reflectivity techniques. In sodium deficient samples, the optical absorption peak associated to the fundamental electronic

  6. Electronic and optical properties of nanocrystalline WO3 thin films studied by optical spectroscopy and density functional calculations

    International Nuclear Information System (INIS)

    Johansson, Malin B; Niklasson, Gunnar A; Österlund, Lars; Baldissera, Gustavo; Persson, Clas; Valyukh, Iryna; Arwin, Hans

    2013-01-01

    The optical and electronic properties of nanocrystalline WO 3 thin films prepared by reactive dc magnetron sputtering at different total pressures (P tot ) were studied by optical spectroscopy and density functional theory (DFT) calculations. Monoclinic films prepared at low P tot show absorption in the near infrared due to polarons, which is attributed to a strained film structure. Analysis of the optical data yields band-gap energies E g ≈ 3.1 eV, which increase with increasing P tot by 0.1 eV, and correlate with the structural modifications of the films. The electronic structures of triclinic δ-WO 3 , and monoclinic γ- and ε-WO 3 were calculated using the Green function with screened Coulomb interaction (GW approach), and the local density approximation. The δ-WO 3 and γ-WO 3 phases are found to have very similar electronic properties, with weak dispersion of the valence and conduction bands, consistent with a direct band-gap. Analysis of the joint density of states shows that the optical absorption around the band edge is composed of contributions from forbidden transitions (>3 eV) and allowed transitions (>3.8 eV). The calculations show that E g in ε-WO 3 is higher than in the δ-WO 3 and γ-WO 3 phases, which provides an explanation for the P tot dependence of the optical data. (paper)

  7. Electronic and optical properties of nanocrystalline WO3 thin films studied by optical spectroscopy and density functional calculations

    Science.gov (United States)

    Johansson, Malin B.; Baldissera, Gustavo; Valyukh, Iryna; Persson, Clas; Arwin, Hans; Niklasson, Gunnar A.; Österlund, Lars

    2013-05-01

    The optical and electronic properties of nanocrystalline WO3 thin films prepared by reactive dc magnetron sputtering at different total pressures (Ptot) were studied by optical spectroscopy and density functional theory (DFT) calculations. Monoclinic films prepared at low Ptot show absorption in the near infrared due to polarons, which is attributed to a strained film structure. Analysis of the optical data yields band-gap energies Eg ≈ 3.1 eV, which increase with increasing Ptot by 0.1 eV, and correlate with the structural modifications of the films. The electronic structures of triclinic δ-WO3, and monoclinic γ- and ε-WO3 were calculated using the Green function with screened Coulomb interaction (GW approach), and the local density approximation. The δ-WO3 and γ-WO3 phases are found to have very similar electronic properties, with weak dispersion of the valence and conduction bands, consistent with a direct band-gap. Analysis of the joint density of states shows that the optical absorption around the band edge is composed of contributions from forbidden transitions (>3 eV) and allowed transitions (>3.8 eV). The calculations show that Eg in ε-WO3 is higher than in the δ-WO3 and γ-WO3 phases, which provides an explanation for the Ptot dependence of the optical data.

  8. A toolkit for detecting technical surprise.

    Energy Technology Data Exchange (ETDEWEB)

    Trahan, Michael Wayne; Foehse, Mark C.

    2010-10-01

    The detection of a scientific or technological surprise within a secretive country or institute is very difficult. The ability to detect such surprises would allow analysts to identify the capabilities that could be a military or economic threat to national security. Sandia's current approach utilizing ThreatView has been successful in revealing potential technological surprises. However, as data sets become larger, it becomes critical to use algorithms as filters along with the visualization environments. Our two-year LDRD had two primary goals. First, we developed a tool, a Self-Organizing Map (SOM), to extend ThreatView and improve our understanding of the issues involved in working with textual data sets. Second, we developed a toolkit for detecting indicators of technical surprise in textual data sets. Our toolkit has been successfully used to perform technology assessments for the Science & Technology Intelligence (S&TI) program.

  9. Energy modulation of nonrelativistic electrons in an optical near field on a metal microslit

    Science.gov (United States)

    Ishikawa, R.; Bae, J.; Mizuno, K.

    2001-04-01

    Energy modulation of nonrelativistic electrons with a laser beam using a metal microslit as an interaction circuit has been investigated. An optical near field is induced in the proximity of the microslit by illumination of the laser beam. The electrons passing close to the slit are accelerated or decelerated by an evanescent wave contained in the near field whose phase velocity is equal to the velocity of the electrons. The electron-evanescent wave interaction in the microslit has been analyzed theoretically and experimentally. The theory has predicted that electron energy can be modulated at optical frequencies. Experiments performed in the infrared region have verified theoretical predictions. The electron-energy changes of more than ±5 eV with a 10 kW CO2 laser pulse at the wavelength of 10.6 μm has been successfully observed for an electron beam with an energy of less than 80 keV.

  10. X rays and radioactivity: a complete surprise

    International Nuclear Information System (INIS)

    Radvanyi, P.; Bordry, M.

    1995-01-01

    The discoveries of X rays and of radioactivity came as complete experimental surprises; the physicists, at that time, had no previous hint of a possible structure of atoms. It is difficult now, knowing what we know, to replace ourselves in the spirit, astonishment and questioning of these years, between 1895 and 1903. The nature of X rays was soon hypothesized, but the nature of the rays emitted by uranium, polonium and radium was much more difficult to disentangle, as they were a mixture of different types of radiations. The origin of the energy continuously released in radioactivity remained a complete mystery for a few years. The multiplicity of the radioactive substances became soon a difficult matter: what was real and what was induced ? Isotopy was still far ahead. It appeared that some radioactive substances had ''half-lifes'': were they genuine radioactive elements or was it just a transitory phenomenon ? Henri Becquerel (in 1900) and Pierre and Marie Curie (in 1902) hesitated on the correct answer. Only after Ernest Rutherford and Frederick Soddy established that radioactivity was the transmutation of one element into another, could one understand that a solid element transformed into a gaseous element, which in turn transformed itself into a succession of solid radioactive elements. It was only in 1913 - after the discovery of the atomic nucleus -, through precise measurements of X ray spectra, that Henry Moseley showed that the number of electrons of a given atom - and the charge of its nucleus - was equal to its atomic number in the periodic table. (authors)

  11. X rays and radioactivity: a complete surprise

    Energy Technology Data Exchange (ETDEWEB)

    Radvanyi, P. [Laboratoire National Saturne, Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France); Bordry, M. [Institut du Radium, 75 - Paris (France)

    1995-12-31

    The discoveries of X rays and of radioactivity came as complete experimental surprises; the physicists, at that time, had no previous hint of a possible structure of atoms. It is difficult now, knowing what we know, to replace ourselves in the spirit, astonishment and questioning of these years, between 1895 and 1903. The nature of X rays was soon hypothesized, but the nature of the rays emitted by uranium, polonium and radium was much more difficult to disentangle, as they were a mixture of different types of radiations. The origin of the energy continuously released in radioactivity remained a complete mystery for a few years. The multiplicity of the radioactive substances became soon a difficult matter: what was real and what was induced ? Isotopy was still far ahead. It appeared that some radioactive substances had ``half-lifes``: were they genuine radioactive elements or was it just a transitory phenomenon ? Henri Becquerel (in 1900) and Pierre and Marie Curie (in 1902) hesitated on the correct answer. Only after Ernest Rutherford and Frederick Soddy established that radioactivity was the transmutation of one element into another, could one understand that a solid element transformed into a gaseous element, which in turn transformed itself into a succession of solid radioactive elements. It was only in 1913 - after the discovery of the atomic nucleus -, through precise measurements of X ray spectra, that Henry Moseley showed that the number of electrons of a given atom - and the charge of its nucleus - was equal to its atomic number in the periodic table. (authors).

  12. Half-period optical pulse generation using a free-electron laser

    International Nuclear Information System (INIS)

    Jaroszynski, D.A.; Chaix, P.; Piovella, N.

    1995-01-01

    Recently there has been growth, in interest in non-equilibrium interaction of half-period long optical pulses with matter. To date the optical pulses have been produced by chopping out a half-period long segment from a longer pulse using a semiconductor switch driven by a femtosecond laser. In this paper we present new methods for producing tunable ultra-short optical pulses as short as half an optical period using a free-electron laser driven by electron bunches with a duration a fraction of an optical period. Two different methods relying on the production of coherent spontaneous emission will be described. In the first method we show that when a train of ultra-short optical pulses as short as one half period. We present calculations which show that the small signal gain is unimportant in the early stages of radiation build up in the cavity when the startup process is dominated by coherent spontaneous emission. To support our proposed method we present encouraging experimental results from the FELIX experiment in the Netherlands which show that interference effects between the coherent spontaneous optical pulses at start-up are very important. The second proposed method relies on the fact that coherent spontaneous emission mimics the undulations of electrons as they pass through the undulator. We show that ultra-short optical pulses are produced by coherent spontaneous emission when ultra-short electron bunches pass through an ultra-short undulator. We discuss the interesting case of such undulator radiation in the presence of an optical cavity and show that the optical pulse can be open-quotes tayloredclose quotes by simply adjusting the optical cavity desynchronism. The proposed methods may be realisable using existing rf driven FELs in the far-infrared

  13. Electron beam excitation assisted optical microscope with ultra-high resolution.

    Science.gov (United States)

    Inami, Wataru; Nakajima, Kentaro; Miyakawa, Atsuo; Kawata, Yoshimasa

    2010-06-07

    We propose electron beam excitation assisted optical microscope, and demonstrated its resolution higher than 50 nm. In the microscope, a light source in a few nanometers size is excited by focused electron beam in a luminescent film. The microscope makes it possible to observe dynamic behavior of living biological specimens in various surroundings, such as air or liquids. Scan speed of the nanometric light source is faster than that in conventional near-field scanning optical microscopes. The microscope enables to observe optical constants such as absorption, refractive index, polarization, and their dynamic behavior on a nanometric scale. The microscope opens new microscopy applications in nano-technology and nano-science.

  14. Electronic, bonding, linear and non-linear optical properties of novel Li{sub 2}Ga{sub 2}GeS{sub 6} compound

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Wilayat, E-mail: wkhan@ntc.zcu.cz [New Technologies – Research Center, University of West Bohemia, Univerzitni 8, Pilsen 306 14 (Czech Republic); Murtaza, G., E-mail: murtaza@icp.edu.pk [Department of Physics, Islamia College Peshawar, KPK (Pakistan); Ouahrani, T. [Laboratoire de Physique Théorique, B.P. 230, Université de Tlemcen, Tlemcen 13000 (Algeria); École Préparatoire en Sciences et Techniques, BP 165 R.P., 13000 Tlemcen (Algeria); Mahmood, Asif [College of Engineering, Chemical Engineering Department, King Saud University Riyadh (Saudi Arabia); Khenata, R.; El Amine Monir, Mohammed; Baltache, H. [Laboratoire de Physique Quantique, de la Matière et de la Modélisation Mathématique (LPQ3M), Université de Mascara, Mascara 29000 (Algeria)

    2016-07-25

    Recently a new sulphide compound Li{sub 2}Ga{sub 2}GeS{sub 6} was synthesized. It has attracted great attention due to its nonlinear optical properties. Quite surprisingly no theoretical study yet been reported on the physical properties of this important material. We have paid attention to study the electronic and optical properties of Li{sub 2}Ga{sub 2}GeS{sub 6} using first principles techniques of density functional theory. Different exchange-correlation techniques have been applied to study these properties. From local density and generalized gradient approximations the compound is predicted to be direct bandgap. However the band gap is indirect when calculated through the Engle–Vosko and modified Becke–Johnson potentials. Therefore the bandgap of the compound is pseudo direct (direct and indirect band gaps are very close). In optical properties dielectric function, refractive index, reflectivity and absorption coefficient were studied. Furthermore, the second harmonic generation properties of the compound are predicted. - Highlights: • Li{sub 2}Ga{sub 2}GeS{sub 6} studied for the first time using first principles calculations. • Different exchange correlation potentials have been adopted for the calculations. • Bandgap of the compound is pseudo direct. • Optical structures are prominent in the low frequency ultraviolet region. • The lone pair basins seem to have a non-negligible role in the optical properties.

  15. Electronic structure and optical properties of thorium monopnictides

    Indian Academy of Sciences (India)

    We have calculated the electronic density of states (DOS) and dielectric function for the ThX (X = P, As and Sb) using the linear muffin tin orbital method within atomic sphere approximation (LMTO–ASA) including the combined correction terms. The calculated electronic DOS of ThSb has been compared with the available ...

  16. The Need for Optical Means as an Alternative for Electronic Computing

    Science.gov (United States)

    Adbeldayem, Hossin; Frazier, Donald; Witherow, William; Paley, Steve; Penn, Benjamin; Bank, Curtis; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    An increasing demand for faster computers is rapidly growing to encounter the fast growing rate of Internet, space communication, and robotic industry. Unfortunately, the Very Large Scale Integration technology is approaching its fundamental limits beyond which the device will be unreliable. Optical interconnections and optical integrated circuits are strongly believed to provide the way out of the extreme limitations imposed on the growth of speed and complexity of nowadays computations by conventional electronics. This paper demonstrates two ultra-fast, all-optical logic gates and a high-density storage medium, which are essential components in building the future optical computer.

  17. Thermostimulated luminescence in KBr-In crystals after optical creation of electronic excitation

    International Nuclear Information System (INIS)

    Popov, A.I.

    1990-01-01

    Thermal stability of the radiation defects produced in KBr-In by optical creation of the electronic excitation (optical creation of the excitons or optical ionization of In + -ions under C-band illumination) is investigated by the method of thermostimulated luminescence (TSL). A method of detection of prehistory defects, when the optical ionization of In + -ions and TSL are performed, is proposed. Quadratic dependence of V 2 -center creation upon dose is shown. This dependence confirms assocative mechanism of the creation of V 2 -centers from two interstitial centers

  18. Electro-optic spatial decoding on the spherical-wavefront Coulomb fields of plasma electron sources.

    Science.gov (United States)

    Huang, K; Esirkepov, T; Koga, J K; Kotaki, H; Mori, M; Hayashi, Y; Nakanii, N; Bulanov, S V; Kando, M

    2018-02-13

    Detections of the pulse durations and arrival timings of relativistic electron beams are important issues in accelerator physics. Electro-optic diagnostics on the Coulomb fields of electron beams have the advantages of single shot and non-destructive characteristics. We present a study of introducing the electro-optic spatial decoding technique to laser wakefield acceleration. By placing an electro-optic crystal very close to a gas target, we discovered that the Coulomb field of the electron beam possessed a spherical wavefront and was inconsistent with the previously widely used model. The field structure was demonstrated by experimental measurement, analytic calculations and simulations. A temporal mapping relationship with generality was derived in a geometry where the signals had spherical wavefronts. This study could be helpful for the applications of electro-optic diagnostics in laser plasma acceleration experiments.

  19. Wave Optical Calculation of Probe Size in Low Energy Scanning Electron Microscope

    Czech Academy of Sciences Publication Activity Database

    Radlička, Tomáš

    2015-01-01

    Roč. 21, S4 (2015), s. 212-217 ISSN 1431-9276 R&D Projects: GA MŠk(CZ) LO1212 Institutional support: RVO:68081731 Keywords : scanning electron microscope * optical calculation Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.730, year: 2015

  20. Optical emission from a high-refractive-index waveguide excited by a traveling electron beam

    International Nuclear Information System (INIS)

    Kuwamura, Yuji; Yamada, Minoru; Okamoto, Ryuichi; Kanai, Takeshi; Fares, Hesham

    2008-01-01

    An optical emission scheme was demonstrated, in which a high-refractive-index waveguide is excited by a traveling electron beam in a vacuum environment. The waveguide was made of Si-SiO 2 layers. The velocity of light propagating in the waveguide was slowed down to 1/3 of that in free space due to the high refractive index of Si. The light penetrated partly into the vacuum in the form of a surface wave. The electron beam was emitted from an electron gun and propagated along the surface of the waveguide. When the velocity of the electron coincided with that of the light, optical emission was observed. This emission is a type of Cherenkov radiation and is not conventional cathode luminescence from the waveguide materials because Si and SiO 2 are transparent to light at the emitted wavelength. This type of emission was observed in an optical wavelength range from 1.2 to 1.6 μm with an electron acceleration voltage of 32-42 kV. The characteristics of the emitted light, such as the polarization direction and the relation between the acceleration voltage of the electron beam and the optical wavelength, coincided well with the theoretical results. The coherent length of an electron wave in the vacuum was confirmed to be equal to the electron spacing, as found by measuring the spectral profile of the emitted light

  1. Simulation of Space Charge Effects in Electron Optical System Based on the Calculations of Current Density

    Czech Academy of Sciences Publication Activity Database

    Zelinka, Jiří; Oral, Martin; Radlička, Tomáš

    2015-01-01

    Roč. 21, S4 (2015), s. 246-251 ISSN 1431-9276 R&D Projects: GA MŠk(CZ) LO1212 Institutional support: RVO:68081731 Keywords : electron optical system * calculations of current density Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.730, year: 2015

  2. Measurement of single electron and nuclear spin states based on optically detected magnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Berman, Gennady P [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Bishop, Alan R [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Chernobrod, Boris M [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Hawley, Marilyn E [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Brown, Geoffrey W [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Tsifrinovich, Vladimir I [Polytechnic University, Brooklyn, NY 11201 (United States)

    2006-05-15

    A novel approach for measurement of single electron and nuclear spin states is suggested. Our approach is based on optically detected magnetic resonance in a nano-probe located at the apex of an AFM tip. The method provides single electron spin sensitivity with nano-scale spatial resolution.

  3. Measurement of single electron and nuclear spin states based on optically detected magnetic resonance

    International Nuclear Information System (INIS)

    Berman, Gennady P; Bishop, Alan R; Chernobrod, Boris M; Hawley, Marilyn E; Brown, Geoffrey W; Tsifrinovich, Vladimir I

    2006-01-01

    A novel approach for measurement of single electron and nuclear spin states is suggested. Our approach is based on optically detected magnetic resonance in a nano-probe located at the apex of an AFM tip. The method provides single electron spin sensitivity with nano-scale spatial resolution

  4. Fifty years old, and still going strong: Transmission electron optical studies of materials

    International Nuclear Information System (INIS)

    Brown, L.M.

    2008-01-01

    Highlights in the history of transmission electron microscopy and scanning transmission electron microscopy include the introduction of diffraction contrast, resolution of periodic lattices by phase contrast and incoherent imaging via the high-angle annular dark-field detector. Convergent-beam electron diffraction and analytical electron microscopy, especially the application of energy-dispersive X-ray and electron energy-loss spectrometry, have provided structural and chemical information in addition to strain contrast from lattice defects. From the outset, novel specimen stages and improvements to aid the operator enhanced the electron-optical engineering provided by the instrument makers. The spatial resolution achieved was mainly determined by the way the instrument was used, and not by the basic resolution limit set by the electron optics. However, the application of computer controlled correction of spherical (and higher order) aberration has resulted in a new generation of instruments capable of sub-Angstrom point-to-point resolution. This improved performance, combined with electron energy-loss spectrometry, promises genuine three-dimensional determination of atomic and electronic structure: an indispensable weapon in the battle to fabricate and control useful nanostructures. The uncertainty principle now fundamentally restricts some of the observations one can make, but much more technical development over the next decades must occur before one can say that the techniques of electron-optical imaging of material structure have reached their fundamental limitations. One can expect remarkable progress over the next few years

  5. Electronic and optical properties of 2D graphene-like ZnS: DFT calculations

    International Nuclear Information System (INIS)

    Lashgari, Hamed; Boochani, Arash; Shekaari, Ashkan; Solaymani, Shahram; Sartipi, Elmira; Mendi, Rohollah Taghavi

    2016-01-01

    Graphical abstract: - Highlights: • DFT has been applied to investigate the optical properties of 2D-ZnS and 3D-ZnS. • The electronic and the optical properties of 3D-ZnS and 2D-ZnS are compared. • At visible range of energies the transparency of 2D-ZnS is more than the 3D. - Abstract: Density-functional theory has been applied to investigate the electronic and optical properties of graphene-like two-dimensional ZnS in the (0001) direction of its Wurtzite phase. A comparison with 3D-ZnS has been carried out within the PBE- and EV-GGA. The electronic properties of 2D- and 3D-ZnS have been derived by the examination of the electronic band structures and density of states. The optical properties have been determined through the study of the dielectric function, reflectivity, electron loss function, refractive and extinction indices, the absorption index and optical conductivity. It is found that the transparency of 2D-ZnS is greater than the 3D over the visible range. A thorough study of the dielectric function has been performed so that the peaks and the transition bands have been specified. The electron loss function demonstrates that the plasmonic frequency for 2D- and 3D-ZnS is accrued at 11.22 and 19.93 eV within the PBE-GGA, respectively.

  6. Quantum computers based on electron spins controlled by ultrafast off-resonant single optical pulses.

    Science.gov (United States)

    Clark, Susan M; Fu, Kai-Mei C; Ladd, Thaddeus D; Yamamoto, Yoshihisa

    2007-07-27

    We describe a fast quantum computer based on optically controlled electron spins in charged quantum dots that are coupled to microcavities. This scheme uses broadband optical pulses to rotate electron spins and provide the clock signal to the system. Nonlocal two-qubit gates are performed by phase shifts induced by electron spins on laser pulses propagating along a shared waveguide. Numerical simulations of this scheme demonstrate high-fidelity single-qubit and two-qubit gates with operation times comparable to the inverse Zeeman frequency.

  7. Electron-optical system of 200 kV gun for the VEPP-5 preinjector

    International Nuclear Information System (INIS)

    Akimov, V.E.; Kazarezov, I.V.; Tiunov, M.A.

    2004-01-01

    The electron gun with a new electron-optical system to match project parameters of the VEPP-5 preinjector is described. The gun produces the current with 10 A amplitude, pulse duration 2...3 ns at half-height and electron energy 200 keV. The gun has a dispenser cathode 20 mm in diameter and 100 mm spherical radius. The current control is performed by means of molybdenum equipotential grid with the cell size 0.4 centre dot 0.4 mm and optical transparency of about 0.68. The experimental results obtained are in good agreement with project parameters

  8. Measurement of optically and thermally stimulated electron emission from natural minerals

    DEFF Research Database (Denmark)

    Ankjærgaard, C.; Murray, A.S.; Denby, P.M.

    2006-01-01

    to a Riso TL/OSL reader, enabling optically stimulated electrons (OSE) and thermally stimulated electrons (TSE) to be measured simultaneously with optically stimulated luminescence (OSL) and thermoluminescence (TL). Repeated irradiation and measurement is possible without removing the sample from...... the counting chamber. Using this equipment both OSE and TSE from loose sand-sized grains of natural minerals has been recorded. It is shown that both the surface electron traps (giving rise to the OSE signals) and the bulk traps (giving rise to OSL) have the same dosimetric properties. A comparison of OSL...

  9. Long-wavelength optical phonon behavior in uniaxial strained graphene: Role of electron-phonon interaction

    OpenAIRE

    Assili, Mohamed; Haddad, Sonia

    2014-01-01

    We derive the frequency shifts and the broadening of $\\Gamma$ point longitudinal optical (LO) and transverse optical (TO) phonon modes, due to electron-phonon interaction, in graphene under uniaxial strain as a function of the electron density and the disorder amount. We show that, in the absence of a shear strain component, such interaction gives rise to a lifting of the degeneracy of the LO and TO modes which contributes to the splitting of the G Raman band. The anisotropy of the electronic...

  10. Study of electron-beam-evaporated MgO films using electron diffraction, optical absorption and cathodoluminescence

    Energy Technology Data Exchange (ETDEWEB)

    Aboelfotoh, M.O.; Ramsey, J.N.

    1982-05-21

    Reflection high energy electron diffraction, optical absorption and cathodoluminescence were used to study MgO films deposited onto fused silica, single-crystal silicon and LiF substrates at various temperatures. Results showed that some of the same optical absorption and emission bands observed in X- or UV-irradiated, additively colored or mechanically deformed MgO crystals were observed in evaporated MgO films. The peak positions and the relative peak intensities of the optical absorption and emission bands depended on the substrate temperature during film deposition as well as on the structure of the film. The effect of heating the films in air and vacuum on the optical absorption and emission bands is also discussed.

  11. Proton disorder in cubic ice: Effect on the electronic and optical properties

    International Nuclear Information System (INIS)

    Garbuio, Viviana; Pulci, Olivia; Cascella, Michele; Kupchak, Igor; Seitsonen, Ari Paavo

    2015-01-01

    The proton disorder in ice has a key role in several properties such as the growth mode, thermodynamical properties, and ferroelectricity. While structural phase transitions from proton disordered to proton ordered ices have been extensively studied, much less is known about their electronic and optical properties. Here, we present ab initio many body perturbation theory-based calculations of the electronic and optical properties of cubic ice at different levels of proton disorder. We compare our results with those from liquid water, that acts as an example of a fully (proton- and oxygen-)disordered system. We find that by increasing the proton disorder, a shrinking of the electronic gap occurs in ice, and it is smallest in the liquid water. Simultaneously, the excitonic binding energy decreases, so that the final optical gaps result to be almost independent on the degree of proton disorder. We explain these findings as an interplay between the local dipolar disorder and the electronic correlation

  12. Electron-Beam Produced Air Plasma: Optical Measurement of Beam Current

    Science.gov (United States)

    Vidmar, Robert; Stalder, Kenneth; Seeley, Megan

    2006-10-01

    Experiments to quantify the electron beam current and distribution of beam current in air plasma are discussed. The air plasma is produced by a 100-keV 10-mA electron beam source that traverses a transmission window into a chamber with air as a target gas. Air pressure is between 1 mTorr and 760 Torr. Strong optical emissions due to electron impact ionization are observed for the N2 2^nd positive line at 337.1 nm and the N2^+ 1^st negative line at 391.4 nm. Calibration of optical emissions using signals from the isolated transmission window and a Faraday plate are discussed. The calibrated optical system is then used to quantify the electron distribution in the air plasma.

  13. Optical circular deflector with attosecond resolution for ultrashort electron beam

    Directory of Open Access Journals (Sweden)

    Zhen Zhang

    2017-05-01

    Full Text Available A novel method using high-power laser as a circular deflector is proposed for the measurement of femtosecond (fs and sub-fs electron beam. In the scheme, the electron beam interacts with a laser pulse operating in a radially polarized doughnut mode (TEM_{01^{*}} in a helical undulator, generating angular kicks along the beam in two directions at the same time. The phase difference between the two angular kicks makes the beam form a ring after a propagation section with appropriate phase advance, which can reveal the current profile of the electron beam. Detailed theoretical analysis of the method and numerical results with reasonable parameters are both presented. It is shown that the temporal resolution can reach up to ∼100 attosecond, which is a significant improvement for the diagnostics of ultrashort electron beam.

  14. Optical Thermal Characterization Enables High-Performance Electronics Applications

    Energy Technology Data Exchange (ETDEWEB)

    2016-02-01

    NREL developed a modeling and experimental strategy to characterize thermal performance of materials. The technique provides critical data on thermal properties with relevance for electronics packaging applications. Thermal contact resistance and bulk thermal conductivity were characterized for new high-performance materials such as thermoplastics, boron-nitride nanosheets, copper nanowires, and atomically bonded layers. The technique is an important tool for developing designs and materials that enable power electronics packaging with small footprint, high power density, and low cost for numerous applications.

  15. Optical absorption and electron spin resonance studies of Cu in ...

    Indian Academy of Sciences (India)

    Unknown

    Na2O–50B2O3–10As2O3 glasses. In this paper, we report the ESR and optical absorption spectra of Cu2+ ions in xLi2O–(40 – x)Na2O–50B2O3–. 10As2O3 glasses. The values of x were adjusted so that the compositional parameter defined as ...

  16. Surprise: a belief or an emotion?

    Science.gov (United States)

    Mellers, Barbara; Fincher, Katrina; Drummond, Caitlin; Bigony, Michelle

    2013-01-01

    Surprise is a fundamental link between cognition and emotion. It is shaped by cognitive assessments of likelihood, intuition, and superstition, and it in turn shapes hedonic experiences. We examine this connection between cognition and emotion and offer an explanation called decision affect theory. Our theory predicts the affective consequences of mistaken beliefs, such as overconfidence and hindsight. It provides insight about why the pleasure of a gain can loom larger than the pain of a comparable loss. Finally, it explains cross-cultural differences in emotional reactions to surprising events. By changing the nature of the unexpected (from chance to good luck), one can alter the emotional reaction to surprising events. Copyright © 2013 Elsevier B.V. All rights reserved.

  17. Electronic and optical properties of ZrB12 and YB6. Discussion on electron-phonon coupling

    International Nuclear Information System (INIS)

    Teyssier, J.; Kuzmenko, A.; Marel, D. van der; Lortz, R.; Junod, A.; Filippov, V.; Shitsevalova, N.

    2006-01-01

    We report the optical properties of high-quality single crystals of low temperature superconductors zirconiumdodecaboride ZrB 12 (T c =5.95 K) and yttrium hexaboride YB 6 (T c =7.15 K) in the range 6 meV-4.6 eV at room temperature. The experimental optical conductivity was extracted from the analysis of the reflectivity in the infrared range and ellipsometry measurement of the dielectric function in the visible range. The electronic band structure of these compounds was calculated by the self-consistent full-potential LMTO method and used to compute the interband part of the optical conductivity and the plasma frequency Ω p . A good agreement was observed between the interband part of the experimental optical conductivities and the band structure calculations. Different methods combining optical spectroscopy, resistivity, specific heat measurements and results of band structure calculations are used to determine the electron-phonon coupling constant. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. An automatic chip structure optical inspection system for electronic components

    Science.gov (United States)

    Song, Zhichao; Xue, Bindang; Liang, Jiyuan; Wang, Ke; Chen, Junzhang; Liu, Yunhe

    2018-01-01

    An automatic chip structure inspection system based on machine vision is presented to ensure the reliability of electronic components. It consists of four major modules, including a metallographic microscope, a Gigabit Ethernet high-resolution camera, a control system and a high performance computer. An auto-focusing technique is presented to solve the problem that the chip surface is not on the same focusing surface under the high magnification of the microscope. A panoramic high-resolution image stitching algorithm is adopted to deal with the contradiction between resolution and field of view, caused by different sizes of electronic components. In addition, we establish a database to storage and callback appropriate parameters to ensure the consistency of chip images of electronic components with the same model. We use image change detection technology to realize the detection of chip images of electronic components. The system can achieve high-resolution imaging for chips of electronic components with various sizes, and clearly imaging for the surface of chip with different horizontal and standardized imaging for ones with the same model, and can recognize chip defects.

  19. Optically isolated electronic trigger system for experiments on a subnanosecond time scale with a pulsed Van de Graaff electron accelerator

    International Nuclear Information System (INIS)

    Luthjens, L.H.; Vermeulen, M.J.W.; Hom, M.L.

    1980-01-01

    An optically isolated electronic trigger system for a pulsed Van de Graaff electron accelerator, producing an external pretrigger pulse 75 ns before arrival of the electron pulse at the target, is described. The total time jitter between trigger signal and electron pulse is 50 ps. The measurement of optical and electrical transients on a subnanosecond time scale with a sequential sampling oscilloscope is demonstrated. The contribution of various parts of the equipment to the total jitter is discussed. Those contributions to the jitter due to the electron transit time fluctuations in the accelerator assuming a constant acceleration voltage gradient and to the shot noise in the photomultiplier detector of the trigger system are calculated to be 5 ps and 12 to 21 ps respectively. Comparison with the experimental results leads to the conclusion that a considerable part of the total jitter may be attributed to acceleration voltage gradient fluctuations, to accelerator vibrations and possibly to density fluctuations in the insulation gas. Possible improvements of the trigger system are discussed. The apparatus is used for pulse radiolysis experiments with subnanosecond time resolution down to 100 ps in combination with subnanosecond time duration electron pulses

  20. Optical studies of MBE-grown InN nanocolumns: Evidence of surface electron accumulation

    Science.gov (United States)

    Segura-Ruiz, J.; Garro, N.; Cantarero, A.; Denker, C.; Malindretos, J.; Rizzi, A.

    2009-03-01

    Vertically self-aligned InN nanocolumns have been investigated by means of scanning electron microscopy, Raman scattering, and photoluminescence spectroscopy. Different nanocolumn morphologies corresponding to different molecular beam epitaxy growth conditions have been studied. Raman spectra revealed strain-free nanocolumns with high crystalline quality for the full set of samples studied. Longitudinal optical modes both uncoupled and coupled to an electron plasma coexist in the Raman spectra pointing to the existence of two distinctive regions in the nanocolumn: a surface layer of degenerated electrons and a nondegenerated inner core. The characteristics of the low-temperature photoluminescence and its dependence on temperature and excitation power can be explained by a model considering localized holes recombining with degenerated electrons close to the nonpolar surface. The differences observed in the optical response of different samples showing similar crystalline quality have been attributed to the variation in the electron accumulation layer with the growth conditions.

  1. A surprising way to control the charge transport in molecular electronics: the subtle impact of the coverage of self-assembled monolayers of floppy molecules adsorbed on metallic electrodes.

    Science.gov (United States)

    Bâldea, Ioan

    2017-10-26

    Inspired by earlier attempts in organic electronics aiming at controlling charge injection from metals into organic materials by manipulating the Schottky energy barrier using self-assembled monolayers (SAMs), recent experimental and theoretical work in molecular electronics showed that metal-organic interfaces can be controlled via changes in the metal work function that are induced by SAMs. In this paper we indicate a different route to achieve interface-driven control over the charge transfer/transport at the molecular scale. It is based on the fact that, in floppy molecule based SAMs, the molecular conformation can be tuned by varying the coverage of the adsorbate. We demonstrate this effect with the aid of benchmark molecules that are often used to fabricate nanojunctions and consist of two rings that can easily rotate relative to each other. We show that, by varying the coverage of the SAM, the twisting angle φ of the considered molecular species can be modified by a factor of two. Given the fact that the low bias conductance G scales as cos 2  φ, this results in a change in G of over one order of magnitude for the considered molecular species. Tuning the twisting angle by controlling the SAM coverage may be significant, e.g., for current efforts to fabricate molecular switches. Conversely, the lack of control over the local SAM coverage may be problematic for the reproducibility and interpretation of the STM (scanning tunneling microscope) measurements on repeatedly forming single molecule break junctions.

  2. Electronic and optical properties of finite carbon nanotubes in an electric field

    International Nuclear Information System (INIS)

    Chen, R B; Lee, C H; Chang, C P; Lin, M F

    2007-01-01

    The effects, caused by the geometric structure and an electric field (E), on the electronic and optical properties of quasi-zero-dimensional finite carbon nanotubes are explored by employing the tight-binding model coupled with curvature effects. Electronic properties (state energies, symmetry of electronic states, energy spacing and state degeneracy) are significantly affected by the magnitude and the direction of the electric field and the geometric structure (radius, length and chirality). The electric field, by lowering the symmetry of finite carbon nanotubes, modifies the electronic properties. Thus, the optical excitation spectra, excited by electric polarization parallel to the nanotube axis, exhibit rich delta-function-like peaks, which reveal the characteristics of the electronic properties. Therefore it follows that geometric structure and E influence the low-energy absorption spectra, i.e. the change of frequency of the first peak, the alternation of the peak height and the production of the new peaks. There are more absorption peaks when E is oriented closer to the cross-section plane. Moreover, the very complicated optical absorption spectra are characteristic for the individual chiral carbon nanotube due to its specific geometric structure. Above all, the predicted absorption spectra and the associated electronic properties could be verified by optical measurements

  3. Study of warm dense plasma electronic dynamics by optical interferometry

    International Nuclear Information System (INIS)

    Deneuville, F.

    2013-01-01

    The Warm Dense Matter (WDM) regime is characterised by a density close to the solid density and an electron temperature close to the Fermi temperature. In this work, the nonequilibrium Warm Dense Matter is studied during the solid to liquid phase transition induced by an ultra short laser interacting with a solid. A 30 femtosecond time resolution pump-probe experiment (FDI) is set up, yielding to the measurement of the heated sample complex reflectivity for both S and P polarisation. We have determined a criterion based on the measured reflectivities, which permits to control the interface shape of the probed matter. For pump laser fluences around 1 J/cm 2 , the hydrodynamics of the heated matter is studied and experimental results are compared to the two-temperatures code ESTHER. Furthermore, the evolution of the dielectric function at 800 nm and 400 nm is inferred from our measurements on a sub-picosecond time-scale. Within the Drude-Lorentz model for the conduction electrons, the dielectric function yields information such as ionisation state, electronic temperature and electron collision frequency. (author) [fr

  4. In plane optical sensor based on organic electronic devices

    NARCIS (Netherlands)

    Koetse, M.M; Rensing, P.A.; Heck, G.T. van; Sharpe, R.B.A.; Allard, B.A.M.; Wieringa, F.P.; Kruijt, P.G.M.; Meulendijks, N.M.M.; Jansen, H.; Schoo, H.F.M.

    2008-01-01

    Sensors based on organic electronic devices are emerging in a wide range of application areas. Here we present a sensor platform using organic light emitting diodes (OLED) and organic photodiodes (OPD) as active components. By means of lamination and interconnection technology the functional foils

  5. Optical and electrical properties of some electron and proton irradiated polymers

    International Nuclear Information System (INIS)

    Mishra, R.; Tripathy, S.P.; Sinha, D.; Dwivedi, K.K.; Ghosh, S.; Khathing, D.T.; Mueller, M.; Fink, D.; Chung, W.H.

    2000-01-01

    Ion beam treatment studies have been carried out to investigate the potential for improvements in conductivity properties of the polymers Polytetrafluroethylene (PTFE), Polyimide (PI), Polyethyleneterepthalate (PET) and Polypropylene (PP), after 2 MeV electron and 62 MeV proton irradiation. The shift in optical absorption edges as observed by UV-VIS spectra of the irradiated polymers has been correlated to the optical band-gap using Tauc's expression. A decrease in the optical band-gap has been observed in irradiated PP and PTFE, but no considerable change was found for the optical band-gaps of PET and PI. Further AC conductivity measurements confirmed an increase in conductivity in electron irradiated PP

  6. An optical study of multiple NEIAL events driven by low energy electron precipitation

    Directory of Open Access Journals (Sweden)

    J. M. Sullivan

    2008-08-01

    Full Text Available Optical data are compared with EISCAT radar observations of multiple Naturally Enhanced Ion-Acoustic Line (NEIAL events in the dayside cusp. This study uses narrow field of view cameras to observe small-scale, short-lived auroral features. Using multiple-wavelength optical observations, a direct link between NEIAL occurrences and low energy (about 100 eV optical emissions is shown. This is consistent with the Langmuir wave decay interpretation of NEIALs being driven by streams of low-energy electrons. Modelling work connected with this study shows that, for the measured ionospheric conditions and precipitation characteristics, growth of unstable Langmuir (electron plasma waves can occur, which decay into ion-acoustic wave modes. The link with low energy optical emissions shown here, will enable future studies of the shape, extent, lifetime, grouping and motions of NEIALs.

  7. Study of optically thin electron cyclotron emission from TFTR using a Michelson interferometer

    International Nuclear Information System (INIS)

    Stauffer, F.J.; Boyd, D.A.

    1986-01-01

    The TFTR Michelson interferometer, which is used as an electron temperature diagnostic, has a spectral range of 75-540 GHz. This range is adequate for measuring at least the first three cyclotron harmonics, and it spans both optically thick and thin portions of the ECE spectrum. During the most recent opening of the TFTR vacuum vessel, a concave, carbon reflector was installed on the back wall of the vessel, opposite the light collecting optic of the Michelson system. The reflector is designed to prevent the observation of optically thin ECE that originates from a location that is outside the field of view of the light collecting optic. If this is achieved, it should be possible to derive the electron density profile from measurements of either the extraordinary mode third harmonic or the ordinary mode second harmonic. An analysis of ECE spectra that have been measured before and after installation of the reflector is presented

  8. Viral marketing: the use of surprise

    NARCIS (Netherlands)

    Lindgreen, A.; Vanhamme, J.; Clarke, I.; Flaherty, T.B.

    2005-01-01

    Viral marketing involves consumers passing along a company's marketing message to their friends, family, and colleagues. This chapter reviews viral marketing campaigns and argues that the emotion of surprise often is at work and that this mechanism resembles that of word-of-mouth marketing.

  9. Exploration, Novelty, Surprise and Free Energy Minimisation

    Directory of Open Access Journals (Sweden)

    Philipp eSchwartenbeck

    2013-10-01

    Full Text Available This paper reviews recent developments under the free energy principle that introduce a normative perspective on classical economic (utilitarian decision-making based on (active Bayesian inference. It has been suggested that the free energy principle precludes novelty and complexity, because it assumes that biological systems – like ourselves - try to minimise the long-term average of surprise to maintain their homeostasis. However, recent formulations show that minimising surprise leads naturally to concepts such as exploration and novelty bonuses. In this approach, agents infer a policy that minimises surprise by minimising the difference (or relative entropy between likely and desired outcomes, which involves both pursuing the goal-state that has the highest expected utility (often termed ‘exploitation’ and visiting a number of different goal-states (‘exploration’. Crucially, the opportunity to visit new states increases the value of the current state. Casting decision-making problems within a variational framework, therefore, predicts that our behaviour is governed by both the entropy and expected utility of future states. This dissolves any dialectic between minimising surprise and exploration or novelty seeking.

  10. Glial heterotopia of maxilla: A clinical surprise

    Directory of Open Access Journals (Sweden)

    Santosh Kumar Mahalik

    2011-01-01

    Full Text Available Glial heterotopia is a rare congenital mass lesion which often presents as a clinical surprise. We report a case of extranasal glial heterotopia in a neonate with unusual features. The presentation, management strategy, etiopathogenesis and histopathology of the mass lesion has been reviewed.

  11. Analogies in optics and micro electronics selected contributions on recent developments

    CERN Document Server

    Lenstra, Daan

    1990-01-01

    This book gives an account of a number of recent developments in two different subfields of research, optics and micro--electronics. The leading principle in presenting them together in one book is the striking similarity between a variety of notions in these two research areas. We mention in this respect tunneling, quantum interference and localization, which are important concepts in quantummechanics and more specifically in condensed matter physics. Miniaturization in solid state engineering has led to new phenomena in which these concepts play their significant roles. As it is the wave character of electrons which is strongly emphasized in these phenomena one's attention is quite naturally directed to the field of optics in which the above quantum-mechanical notions all seem to have their direct classical wavemechanical counterparts. Both micro--electronics and optics have been and still are in a mode of intensifying activity. The possibilities to technically "translate" devices developed within one resea...

  12. Cerenkov light generated in optical fibres and other light pipes irradiated by electron beams

    International Nuclear Information System (INIS)

    Beddar, A.S.; Mackie, T.R.; Attix, F.H.

    1992-01-01

    The use of a small plastic scintillator coupled to an optical fibre bundle light pipe for the dosimetry of radiotherapy x-ray or electron beams in a phantom has been studied. Under such conditions, some light is generated by the direct action of the radiation on the optical fibres themselves, and this 'background' signal must be correctly accounted for. Electron beams were incident on fused silica optical fibres and other light pipes made of polymethylmethacrylate (PMMA), polystyrene and water. The observed light signal generated in all cases was found to depend strongly on the angle between the electron direction and the light pipe axis, and to correlate well with the angular characteristics uniquely associated with Cerenkov radiation. The use of a parallel fibre bundle light pipe, identical to the one that carries light from the scintillator, offers a suitable means of generating a similar background Cerenkov light signal that can be subtracted to obtain output from the scintillation dosimeter alone. (author)

  13. Electron beam manipulation, injection and acceleration in plasma wakefield accelerators by optically generated plasma density spikes

    Energy Technology Data Exchange (ETDEWEB)

    Wittig, Georg; Karger, Oliver S.; Knetsch, Alexander [Institute of Experimental Physics, University of Hamburg, 22761 Hamburg (Germany); Xi, Yunfeng; Deng, Aihua; Rosenzweig, James B. [Particle Beam Physics Laboratory, UCLA, Los Angeles, CA 90095 (United States); Bruhwiler, David L. [RadiaSoft LLC, Boulder, CO 80304 (United States); RadiaBeam Technologies LLC (United States); Smith, Jonathan [Tech-X UK Ltd, Daresbury, Cheshire WA4 4FS (United Kingdom); Sheng, Zheng-Ming; Jaroszynski, Dino A.; Manahan, Grace G. [Physics Department, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Hidding, Bernhard [Institute of Experimental Physics, University of Hamburg, 22761 Hamburg (Germany); Physics Department, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom)

    2016-09-01

    We discuss considerations regarding a novel and robust scheme for optically triggered electron bunch generation in plasma wakefield accelerators [1]. In this technique, a transversely propagating focused laser pulse ignites a quasi-stationary plasma column before the arrival of the plasma wake. This localized plasma density enhancement or optical “plasma torch” distorts the blowout during the arrival of the electron drive bunch and modifies the electron trajectories, resulting in controlled injection. By changing the gas density, and the laser pulse parameters such as beam waist and intensity, and by moving the focal point of the laser pulse, the shape of the plasma torch, and therefore the generated trailing beam, can be tuned easily. The proposed method is much more flexible and faster in generating gas density transitions when compared to hydrodynamics-based methods, and it accommodates experimentalists needs as it is a purely optical process and straightforward to implement.

  14. Optical modeling of induction-linac driven free-electron lasers

    International Nuclear Information System (INIS)

    Scharlemann, E.T.; Fawley, W.M.

    1986-01-01

    The free-electron laser (FEL) simulation code FRED, developed at Lawrence Livermore National Laboratory (LLNL) primarily to model single-pass FEL amplifiers driven by induction linear accelerators, is described. The main emphasis is on the modeling of optical propagation in the laser and on the differences between the requirements for modeling rf-linac-driven vs. induction-linac-driven FELs. Examples of optical guiding and mode cleanup are presented for a 50 μm FEL

  15. Design of fiber optic electronic seal system based on C8051 microcontroller

    International Nuclear Information System (INIS)

    Di Yuming; Chen Rongye; Zuo Guangxia; Song Cang

    2012-01-01

    This paper presents fiber optic electronic seal system, witch uses C8051 microcontroller as core, matching other circuits such as optical signal detection module, movement detection module, temperature detection module and power module, etc. The results show that the seal system can record the tampering events' information accurately and quickly no matter there is one tamper event or more, and the ability of anti-tamper is improved. (authors)

  16. Research on heightening of performance of optical system for free electron laser

    International Nuclear Information System (INIS)

    Kumagai, Hiroshi; Kawamura, Yoshiyuki; Toyada, Koichi

    1996-01-01

    Free electron laser will become in future the center of industrial laser technology as a high efficiency, high power output laser. For the development of free electron laser, the development of the elementary technologies such as accelerator, wiggler, optical system and so on must be carried out. For the stable functioning of free electron laser for long hours, the innovative technical development of the optical technology has been strongly desired. In this research, the development of the method of manufacturing a new high performance, multilayer film reflection mirror and the research on compound optical damage by new high energy photon generation process were advanced. The research on the formation of aluminum oxide thin films by using surface reaction, the development of the technology for forming high accuracy, multi-layer thin films and the evaluation of the optical performance of multi-layer films are reported. The constitution of compound optical damage evaluation system, the calculation of the luminance of high energy photons and the experiment on the generation of photons by a carbon dioxide gas laser are described regarding the compound optical damage research. (K.I.)

  17. The electronic and optical properties of warm dense nitrous oxide using quantum molecular dynamics simulations

    International Nuclear Information System (INIS)

    Zhang Yujuan; Wang Cong; Zhang Ping

    2012-01-01

    First-principles molecular-dynamics simulations based on density-functional theory have been used to study the electronic and optical properties of fluid nitrous oxide under extreme conditions. Systematic descriptions of pair-correlation function, atomic structure, and the charge density distribution are used to investigate the dissociation of fluid nitrous oxide. The electrical and optical properties are derived from the Kubo-Greenwood formula. It is found that the nonmetal-metal transition for fluid nitrous oxide can be directly associated to the dissociation and has significant influence on the optical properties of the fluid.

  18. Optical Pumping of the Electronic and Nuclear Spin of Single Charge-Tunable Quantum Dots

    Science.gov (United States)

    Bracker, A. S.; Stinaff, E. A.; Gammon, D.; Ware, M. E.; Tischler, J. G.; Shabaev, A.; Efros, Al. L.; Park, D.; Gershoni, D.; Korenev, V. L.; Merkulov, I. A.

    2005-02-01

    We present a comprehensive examination of optical pumping of spins in individual GaAs quantum dots as we change the net charge from positive to neutral to negative with a charge-tunable heterostructure. Negative photoluminescence polarization memory is enhanced by optical pumping of ground state electron spins, which we prove with the first measurements of the Hanle effect on an individual quantum dot. We use the Overhauser effect in a high longitudinal magnetic field to demonstrate efficient optical pumping of nuclear spins for all three charge states of the quantum dot.

  19. Optical radiation emitted by a silver surface bombarded by low-energy electrons

    International Nuclear Information System (INIS)

    Miserey, F.; Lebon, P.; Septier, A.; Trehin, F.; Beaugrand, C.

    1975-01-01

    Thick silver targets are obtained on flat glass discs by evaporation in a UHV cell (p -10 torr) and their optical coefficients measured by ellipsometry. A field-emission electron gun bombards a limited region of the target, corresponding to the entry pupil of a light spectrometer. Radiation emitted in the domain 250-600nm is analyzed for both normal and parallel polarizations. Spectral distributions of photons are obtained by using a very sensitive counting device including a multi channel analyzer. First experimental results concerning optical radiation generated by 6keV electrons are reported and compared to Transition Radiation and Bremsstrahlung theoretical spectra [fr

  20. Quasiparticle electronic and optical properties of the Si-Sn system

    International Nuclear Information System (INIS)

    Jensen, Rasmus V S; Pedersen, Thomas G; Larsen, Arne N

    2011-01-01

    The Si 1-x Sn x material system is an interesting candidate for an optically active material compatible with Si. Based on density functional theory with quasiparticle corrections we calculate the electronic band structure of zinc-blende SiSn under both compressive and tensile strain. At 2.2% tensile strain the band gap becomes direct with a magnitude of 0.85 eV. We develop an accurate tight-binding parameterization of the electronic structure and calculate the optical properties of SiSn. Furthermore, the silicide SiSn 2 is investigated and found to have metallic character. (paper)

  1. Investigation of the electronic, magnetic and optical properties of newest carbon allotrope

    Science.gov (United States)

    Kazemi, Samira; Moradian, Rostam

    2018-05-01

    We investigate triple properties of monolayer pentagon graphene that include electronic, magnetic and optical properties based on density functional theory (DFT). Our results show that in the electronic and magnetic properties this structure with a direct energy gap of about 2.2 eV along Γ - Γ direction and total magnetic moment of 0.0013 μB per unit cell is almost a non-magnetic semiconductor. Also, its optical properties show that if this allotrope used in solar cell technology, its efficiency in the low energy will be better, because, in the range of energy, its loss energy function and reflectivity will be minimum.

  2. Quantum electronics and Moscow State University's Khokhlov-Akhmanov school of coherent and nonlinear optics

    International Nuclear Information System (INIS)

    Makarov, V.A.

    2004-01-01

    The aim of the report is to describe the history of the Moscow University Coherent and Nonlinear Optics School headed by R.V. Khokhlov and S.A. Akhmanov being a part of the history of the Russian efforts to investigate into quantum electronics. The reports describes briefly the most significant results of the mentioned School activity, in particular, thermonuclear reactions initiated by laser pulses in plasma; the procedure to accelerate electrons up to 1 GeV using the present-day lasers; the nonlinear-optical analogues of the Faraday and the Kerr effects [ru

  3. Optical and Electronic NOx Sensors for Applications in Mechatronics

    Directory of Open Access Journals (Sweden)

    Scott D. Wolter

    2009-05-01

    Full Text Available Current production and emerging NOx sensors based on optical and nanomaterials technologies are reviewed. In view of their potential applications in mechatronics, we compared the performance of: i Quantum cascade lasers (QCL based photoacoustic (PA systems; ii gold nanoparticles as catalytically active materials in field-effect transistor (FET sensors, and iii functionalized III-V semiconductor based devices. QCL-based PA sensors for NOx show a detection limit in the sub part-per-million range and are characterized by high selectivity and compact set-up. Electrochemically synthesized gold-nanoparticle FET sensors are able to monitor NOx in a concentration range from 50 to 200 parts per million and are suitable for miniaturization. Porphyrin-functionalized III-V semiconductor materials can be used for the fabrication of a reliable NOx sensor platform characterized by high conductivity, corrosion resistance, and strong surface state coupling.

  4. Optical and Electronic NOx Sensors for Applications in Mechatronics

    Science.gov (United States)

    Di Franco, Cinzia; Elia, Angela; Spagnolo, Vincenzo; Scamarcio, Gaetano; Lugarà, Pietro Mario; Ieva, Eliana; Cioffi, Nicola; Torsi, Luisa; Bruno, Giovanni; Losurdo, Maria; Garcia, Michael A.; Wolter, Scott D.; Brown, April; Ricco, Mario

    2009-01-01

    Current production and emerging NOx sensors based on optical and nanomaterials technologies are reviewed. In view of their potential applications in mechatronics, we compared the performance of: i) Quantum cascade lasers (QCL) based photoacoustic (PA) systems; ii) gold nanoparticles as catalytically active materials in field-effect transistor (FET) sensors, and iii) functionalized III-V semiconductor based devices. QCL-based PA sensors for NOx show a detection limit in the sub part-per-million range and are characterized by high selectivity and compact set-up. Electrochemically synthesized gold-nanoparticle FET sensors are able to monitor NOx in a concentration range from 50 to 200 parts per million and are suitable for miniaturization. Porphyrin-functionalized III-V semiconductor materials can be used for the fabrication of a reliable NOx sensor platform characterized by high conductivity, corrosion resistance, and strong surface state coupling. PMID:22412315

  5. Electron optics with magnetic vector potential barriers in graphene

    International Nuclear Information System (INIS)

    Ghosh, Sankalpa; Sharma, Manish

    2009-01-01

    An analysis of electron transport in graphene in the presence of various arrangements of delta-function like magnetic barriers is presented. The motion through one such barrier gives an unusual non-specular refraction leading to asymmetric transmission. The symmetry is restored by putting two such barriers in opposite directions side by side. Periodic arrangements of such barriers can be used as Bragg reflectors whose reflectivity has been calculated using a transfer matrix formalism. Such Bragg reflectors can be used to make resonant cavities. We also analyze the associated band structure for the case of infinite periodic structures. (fast track communication)

  6. Electron hopping and optic phonons in Eu3S4

    International Nuclear Information System (INIS)

    Guentherodt, G.

    1981-01-01

    Raman scattering on single crystals of Eu 3 S 4 does not show the allowed q=o phonon modes in the cubic phase and exhibits no new modes in the distorted low temperature phase (T 2- ions. This mode does not show any anomaly near the charge order -disorder phase transition Tsub(t)=186 K. Temperature tunable spin fluctuations associated with the temperature activated Eu 2+ → Eu 3+ electron hopping are detected in the scattering intensity, superimposed on the usual thermal spin disorder. (author)

  7. Physics design of the in-vessel collection optics for the ITER electron cyclotron emission diagnostic

    Energy Technology Data Exchange (ETDEWEB)

    Rowan, W. L., E-mail: w.l.rowan@austin.utexas.edu; Houshmandyar, S.; Phillips, P. E.; Austin, M. E. [Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712 (United States); Beno, J. H.; Ouroua, A. [Center for Electromechanics, The University of Texas at Austin, Austin, Texas 78712 (United States); Hubbard, A. E. [Plasma Science and Fusion Center, MIT, Cambridge, Massachusetts 02139 (United States); Khodak, A.; Taylor, G. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

    2016-11-15

    Measurement of the electron cyclotron emission (ECE) is one of the primary diagnostics for electron temperature in ITER. In-vessel, in-vacuum, and quasi-optical antennas capture sufficient ECE to achieve large signal to noise with microsecond temporal resolution and high spatial resolution while maintaining polarization fidelity. Two similar systems are required. One views the plasma radially. The other is an oblique view. Both views can be used to measure the electron temperature, while the oblique is also sensitive to non-thermal distortion in the bulk electron distribution. The in-vacuum optics for both systems are subject to degradation as they have a direct view of the ITER plasma and will not be accessible for cleaning or replacement for extended periods. Blackbody radiation sources are provided for in situ calibration.

  8. Electron spin dynamics and optical orientation of Mn2+ ions in GaAs

    Science.gov (United States)

    Akimov, I. A.; Dzhioev, R. I.; Korenev, V. L.; Kusrayev, Yu. G.; Sapega, V. F.; Yakovlev, D. R.; Bayer, M.

    2013-04-01

    We present an overview of spin-related phenomena in GaAs doped with low concentration of Mn-acceptors (below 1018 cm-3). We use the combination of different experimental techniques such as spin-flip Raman scattering and time-resolved photoluminescence. This allows to evaluate the time evolution of both electron and Mn spins. We show that optical orientation of Mn ions is possible under application of weak magnetic field, which is required to suppress the manganese spin relaxation. The optically oriented Mn2+ ions maintain the spin and return part of the polarization back to the electron spin system providing a long-lived electron spin memory. This leads to a bunch of spectacular effects such as non-exponential electron spin decay and spin precession in the effective exchange fields.

  9. Electronic structures and magnetic/optical properties of metal phthalocyanine complexes

    Energy Technology Data Exchange (ETDEWEB)

    Baba, Shintaro; Suzuki, Atsushi, E-mail: suzuki@mat.usp.ac.jp; Oku, Takeo [Department of Materials Science, The University of Shiga Prefecture. 2500 Hassaka, Hikone, Shiga 522-8533 (Japan)

    2016-02-01

    Electronic structures and magnetic / optical properties of metal phthalocyanine complexes were studied by quantum calculations using density functional theory. Effects of central metal and expansion of π orbital on aromatic ring as conjugation system on the electronic structures, magnetic, optical properties and vibration modes of infrared and Raman spectra of metal phthalocyanines were investigated. Electron and charge density distribution and energy levels near frontier orbital and excited states were influenced by the deformed structures varied with central metal and charge. The magnetic parameters of chemical shifts in {sup 13}C-nuclear magnetic resonance ({sup 13}C-NMR), principle g-tensor, A-tensor, V-tensor of electric field gradient and asymmetry parameters derived from the deformed structures with magnetic interaction of nuclear quadruple interaction based on electron and charge density distribution with a bias of charge near ligand under crystal field.

  10. Imaging photoelectron photoion coincidence spectroscopy with velocity focusing electron optics

    International Nuclear Information System (INIS)

    Bodi, Andras; Johnson, Melanie; Gerber, Thomas; Gengeliczki, Zsolt; Sztaray, Balint; Baer, Tomas

    2009-01-01

    An imaging photoelectron photoion coincidence spectrometer at the vacuum ultraviolet (VUV) beamline of the Swiss Light Source is presented and a few initial measurements are reported. Monochromatic synchrotron VUV radiation ionizes the cooled or thermal gas-phase sample. Photoelectrons are velocity focused, with better than 1 meV resolution for threshold electrons, and also act as start signal for the ion time-of-flight analysis. The ions are accelerated in a relatively low, 40-80 V cm -1 field, which enables the direct measurement of rate constants in the 10 3 -10 7 s -1 range. All electron and ion events are recorded in a triggerless multiple-start/multiple-stop setup, which makes it possible to carry out coincidence experiments at >100 kHz event frequencies. As examples, the threshold photoelectron spectrum of the argon dimer and the breakdown diagrams for hydrogen atom loss in room temperature methane and the chlorine atom loss in cold chlorobenzene are shown and discussed.

  11. Experimental Study of Electronic Quantum Interference, Photonic Crystal Cavity, Photonic Band Edge Effects for Optical Amplification

    Science.gov (United States)

    2016-01-26

    AFRL-RV-PS- AFRL-RV-PS- TR-2016-0003 TR-2016-0003 EXPERIMENTAL STUDY OF ELECTRONIC QUANTUM INTERFERENCE , PHOTONIC CRYSTAL CAVITY, PHOTONIC BAND...EDGE EFFECTS FOR OPTICAL AMPLIFICATION Shawn-Yu Lin Rensselaer Polytechnic Institute 110 8th Street Troy, New York 12180 26 Jan 2016 Final Report...2014 – 11 Jan 2016 4. TITLE AND SUBTITLE Experimental Study of Electronic Quantum Interference , Photonic Crystal Cavity, Photonic Band Edge Effects

  12. Radar Design to Protect Against Surprise

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-02-01

    Technological and doctrinal surprise is about rendering preparations for conflict as irrelevant or ineffective . For a sensor, this means essentially rendering the sensor as irrelevant or ineffective in its ability to help determine truth. Recovery from this sort of surprise is facilitated by flexibility in our own technology and doctrine. For a sensor, this mean s flexibility in its architecture, design, tactics, and the designing organizations ' processes. - 4 - Acknowledgements This report is the result of a n unfunded research and development activity . Sandia National Laboratories is a multi - program laboratory manage d and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE - AC04 - 94AL85000.

  13. Color electron microprobe cathodoluminescence of Bishunpur meteorite compared with the traditional optical microscopy method

    Directory of Open Access Journals (Sweden)

    Amanda Araujo Tosi

    Full Text Available Abstract Cathodoluminescence (CL imaging is an outstanding method for sub classification of Unequilibrated Ordinary Chondrites (UOC - petrological type 3. CL can be obtained by several electron beam apparatuses. The traditional method uses an electron gun coupled to an optical microscope (OM. Although many scanning electron microscopes (SEM and electron microprobes (EPMA have been equipped with a cathodoluminescence, this technique was not fully explored. Images obtained by the two methods differ due to a different kind of signal acquisition. While in the CL-OM optical photography true colors are obtained, in the CL-EPMA the results are grayscale monochromatic electronic signals. L-RGB filters were used in the CL-EPMA analysis in order to obtain color data. The aim of this work is to compare cathodoluminescence data obtained from both techniques, optical microscope and electron microprobe, on the Bishunpur meteorite classified as LL 3.1 chondrite. The present study allows concluding that 20 KeV and 7 nA is the best analytical condition at EPMA in order to test the equivalence between CL-EPMA and CL-OM colour results. Moreover, the color index revealed to be a method for aiding the study of the thermal metamorphism, but it is not definitive for the meteorite classification.

  14. Optically pumped electron spin polarized targets for use in the production of polarized ion beams

    International Nuclear Information System (INIS)

    Anderson, L.W.

    1979-01-01

    The production of relatively dense electron spin polarized alkali metal vapor targets by optical pumping with intense cw dye lasers is discussed. The target density and electron spin polarization depend on the dye laser intensity and bandwidth, the magnetic field at the target, and the electron spin depolarization time. For example in a magnetic field of 1.5 x 10 3 G, and using 1 W dye laser with a bandwidth of 10 10 Hz one can construct an electron spin polarized Na vapor target with a target thickness of 1.6 x 10 13 atoms/cm 2 and an average electron spin polarization of about 90% even though the Na atoms are completely depolarized at every wall collision. Possible uses of the electron spin polarized targets for the production of intense beams of polarized H - or 3 He - ions are discussed. (orig.)

  15. Novel simulation method of space charge effects in electron optical systems including emission of electrons

    Czech Academy of Sciences Publication Activity Database

    Zelinka, Jiří; Oral, Martin; Radlička, Tomáš

    2018-01-01

    Roč. 184, JAN (2018), s. 66-76 ISSN 0304-3991 R&D Projects: GA MŠk(CZ) LO1212; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : space charge * self-consistent simulation * aberration polynomial * electron emission Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 2.843, year: 2016

  16. Electron-optical design parameters for a high-resolution electron monochromator

    International Nuclear Information System (INIS)

    Tanaka, H.; Huebner, R.H.

    1976-01-01

    Detailed design parameters of a new, high-resolution electron monochromator are presented. The design utilizes a hemispherical filter as the energy-dispersing element and combines both cylindrical and aperture electrostatic lenses to accelerate, decelerate, transport, and focus the electron beam from the cathode to the interaction region

  17. Development techniques and electron optical studies of high voltage, high current electron guns

    International Nuclear Information System (INIS)

    Rangarajan, L.M.; Mahadevan, S.; Ramamurthi, S.S.

    1992-01-01

    The progress of the electron gun design, limiting to axially symmetric geometries is discussed here with a view to utilise such guns for electron accelerators. The mechanical design features leading to the physical configuration of the gun with stringent tolerances are outlined. Vacuum processing is done at pressures of 1.3x10 -5 Pa. The gun employs W-filament emitter or a cathode pellet with bombarder service. A water cooled compact faraday cup is used to measure the electron current. Electron gun geometries have been studied using the computer programme. The preveance of the gun is 0.7x10 -7 A/Vsup(1.5) at 80 kV. Developmental techniques of such pulsed electron guns are described. (author). 7 refs., 5 figs

  18. Electronic and optical properties of doped oxides for energy conversion

    International Nuclear Information System (INIS)

    Silva, Antonio Ferreira da

    2016-01-01

    Full text: Photocatalytic materials have gained remarkable attention in the field of solar fuel production, which is a promising approach for efficient solar energy conversion and storage . Among other oxides, doped BiNb(Ta)O 4 , ZnO , SnO 2 , WO 3 and TiO 2 have been identified as potential photocatalytic materials due to their appropriate band gap energies. We have used high quality materials as for instance by the citrate method according to reference [1], a modified ion beam assisted deposition technique [2] and as titanium dioxide nanotubes (TiO 2 -NTs) arrays synthesized by electrochemical anodization [3]. We present the optical properties spectra of these materials using the X-ray Photoelectron Spectroscopy (XPS), Ellipsometry and first principles approach by DFT respectively [1,2]. In this work, position of reduction and oxidation level with respect to the vacuum level are identified for these materials. We can conclude that some of them are good candidates for the production of hydrogen by splitting of water in the presence of sunlight and for efficient solar energy conversion as well. [1] C. G. Almeida, R. B. Araujo, R. G. Yoshimura, A. J. S. Mascarenhas, A. Ferreira da Silva, C. M.Araujo, L. A. Silva,Int. J. Hyd. Energy 39, 1220 (2014). [2] M. Kumar, G.Baldissera, C.Persson, D.G.F.David ,M.V.S.da Silva , J.A.Freitas Jr., J.G. Tischler , J.F.D.Chubaci, M.Matsuoka , A.Ferreira da Silva, , J. of Crystal Growth 403, 124 (2014). [3] J. R. Gonzalez et all., Nanotechnology (2016 in press). (author)

  19. Electronic and optical properties of doped oxides for energy conversion

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Antonio Ferreira da, E-mail: ferreira.fis@gmail.com [Universidade Federal da Bahia (UFBA), Salvador (Brazil)

    2016-07-01

    Full text: Photocatalytic materials have gained remarkable attention in the field of solar fuel production, which is a promising approach for efficient solar energy conversion and storage . Among other oxides, doped BiNb(Ta)O{sub 4}, ZnO , SnO{sub 2}, WO{sub 3} and TiO{sub 2} have been identified as potential photocatalytic materials due to their appropriate band gap energies. We have used high quality materials as for instance by the citrate method according to reference [1], a modified ion beam assisted deposition technique [2] and as titanium dioxide nanotubes (TiO{sub 2}-NTs) arrays synthesized by electrochemical anodization [3]. We present the optical properties spectra of these materials using the X-ray Photoelectron Spectroscopy (XPS), Ellipsometry and first principles approach by DFT respectively [1,2]. In this work, position of reduction and oxidation level with respect to the vacuum level are identified for these materials. We can conclude that some of them are good candidates for the production of hydrogen by splitting of water in the presence of sunlight and for efficient solar energy conversion as well. [1] C. G. Almeida, R. B. Araujo, R. G. Yoshimura, A. J. S. Mascarenhas, A. Ferreira da Silva, C. M.Araujo, L. A. Silva,Int. J. Hyd. Energy 39, 1220 (2014). [2] M. Kumar, G.Baldissera, C.Persson, D.G.F.David ,M.V.S.da Silva , J.A.Freitas Jr., J.G. Tischler , J.F.D.Chubaci, M.Matsuoka , A.Ferreira da Silva, , J. of Crystal Growth 403, 124 (2014). [3] J. R. Gonzalez et all., Nanotechnology (2016 in press). (author)

  20. Optical observations of Magnetosphere-Ionosphere coupling: Inter-hemispheric electron reflections within pulsating aurora

    Science.gov (United States)

    Samara, M.; Michell, R.; Khazanov, G. V.; Grubbs, G. A., II

    2017-12-01

    Magnetosphere-Ionosphere coupling is exhibited in reflected primary and secondary electrons which constitute the second step in the formation of the total precipitating electron distribution. While they have largely been missing from the current theoretical studies of particle precipitation, ground based observations point to the existence of a reflected electron population. We present evidence that pulsating aurora is caused by electrons bouncing back and forth between the two hemispheres. This means that these electrons are responsible for some of the total light in the aurora, a possibility that has largely been ignored in theoretical models. Pulsating auroral events imaged optically at high time resolution present direct observational evidence in agreement with the inter-hemispheric electron bouncing predicted by the SuperThermal Electron Trans-port (STET) model. Immediately following each of the `pulsation-on' times are equally spaced, and subsequently fainter pulsations, which can be explained by the primary precipitating electrons reflecting upwards from the ionosphere, traveling to the opposite hemisphere, and reflecting upwards again. The high time-resolution of these data, combined with the short duration of the `pulsation-on' time ( 1 s) and the relatively long spacing between pulsations ( 6 to 9 s) made it possible to observe the faint optical pulses caused by the reflected electrons coming from the opposite hemisphere. These results are significant and have broad implications because they highlight that the formation of the auroral electron distributions within regions of diffuse and pulsating aurora contain contributions from reflected primary and secondary electrons. These processes can ultimately lead to larger fluxes than expected when considering only the primary injection of magnetospheric electrons.

  1. Optical basicity and electronic polarizability of zinc borotellurite glass doped La3+ ions

    Directory of Open Access Journals (Sweden)

    M.K. Halimah

    Full Text Available Zinc borotellurite glasses doped with lanthanum oxide were successfully prepared through melt-quenching technique. The amorphous nature of the glass system was validated by the presence of a broad hump in the XRD result. The refractive index of the prepared glass samples was calculated by using the equation proposed by Dimitrov and Sakka. The theoretical value of molar refraction, electronic polarizability, oxide ion polarizability and metallization criterion were calculated by using Lorentz-Lorenz equation. Meanwhile, expression proposed by Duffy and Ingram for the theoretical value of optical basicity of multi-component glasses were applied to obtain energy band gap based optical basicity and refractive index based optical basicity. The optical basicity of prepared glasses decreased with the increasing concentration of lanthanum oxide. Metallization criterion on the basis of refractive index showed an increasing trend while energy band gap based metallization criterion showed a decreasing trend. The small metallization criterion values of the glass samples represent that the width of the conduction band becomes larger which increase the tendency for metallization of the glasses. The results obtained indicates that the fabricated glasses have high potential to be applied on optical limiting devices in photonic field. Keywords: Borotellurite glasses, Refractive index, Electronic polarizability, Oxide ion polarizability, Optical basicity, Metallization criterion

  2. Electronic transient processes and optical spectra in quantum dots for quantum computing

    Czech Academy of Sciences Publication Activity Database

    Král, Karel; Zdeněk, Petr; Khás, Zdeněk

    2004-01-01

    Roč. 3, č. 1 (2004), s. 17-25 ISSN 1536-125X R&D Projects: GA AV ČR IAA1010113 Institutional research plan: CEZ:AV0Z1010914 Keywords : depopulation * electronic relaxation * optical spectra * quantum dots * self-assembled quantum dots * upconversion Subject RIV: BE - Theoretical Physics Impact factor: 3.176, year: 2004

  3. Electronic and optical properties of new multifunctional materials via half-substituted hematite: First principles calculations

    KAUST Repository

    Yang, Hua; Mi, Wenbo; Bai, Haili; Cheng, Yingchun

    2012-01-01

    Electronic structure and optical properties of α-FeMO 3 systems (M = Sc, Ti, V, Cr, Cu, Cd or In) have been investigated using first principles calculations. All of the FeMO 3 systems have a large net magnetic moment. The ground state of pure α-Fe 2

  4. New Optical Card for Sneaker’s Network in Place of Electronic Clinical Record

    Science.gov (United States)

    Goto, Kenya; Satsukawa, Takatoshi; Chiba, Seisho; Ohmori, Takaaki

    2006-02-01

    In order to solve problems in electronic medical records, a new optical card of the digital versatile disk (DVD) type with higher capacity and lower cost than conventional compact disc recording (CD-R)-type cards has been developed, which is thinner, stronger and wearable like a credit card.

  5. Optically Controlled Electron-Transfer Reaction Kinetics and Solvation Dynamics : Effect of Franck-Condon States

    NARCIS (Netherlands)

    Gupta, Kriti; Patra, Aniket; Dhole, Kajal; Samanta, Alok Kumar; Ghosh, Swapan K.

    2017-01-01

    Experimental results for optically controlled electron-transfer reaction kinetics (ETRK) and nonequilibrium solvation dynamics (NESD) of Coumarin 480 in DMPC vesicle show their dependence on excitation wavelength λex. However, the celebrated Marcus theory and linear-response-theory-based approaches

  6. The fully relativistic foundation of linear transfer theory in electron optics based on the Dirac equation

    NARCIS (Netherlands)

    Ferwerda, H.A.; Hoenders, B.J.; Slump, C.H.

    The fully relativistic quantum mechanical treatment of paraxial electron-optical image formation initiated in the previous paper (this issue) is worked out and leads to a rigorous foundation of the linear transfer theory. Moreover, the status of the relativistic scaling laws for mass and wavelength,

  7. Electronic and optical properties of antiferromagnetic iron doped NiO - A first principles study

    Science.gov (United States)

    Petersen, John E.; Twagirayezu, Fidele; Scolfaro, Luisa M.; Borges, Pablo D.; Geerts, Wilhelmus J.

    2017-05-01

    Antiferromagnetic NiO is a candidate for next generation high-speed and scaled RRAM devices. Here, electronic and optical properties of antiferromagnetic NiO: Fe 25% in the rock salt structure are studied and compared to intrinsic NiO. From density of states and complex dielectric function analysis, the first optical transition is found to be at lower frequency than intrinsic NiO due to an Fe impurity level being the valence band maximum. The resulting effects on refractive index, reflectivity, absorption, optical conductivity and loss function for Fe-doped NiO are compared to those of intrinsic NiO, and notable differences are analyzed. The electronic component of the static dielectric constant of NiO: Fe 25% is calculated to be about 2% less than that of intrinsic NiO.

  8. Electron irradiation response on Ge and Al-doped SiO{sub 2} optical fibres

    Energy Technology Data Exchange (ETDEWEB)

    Yaakob, N.H.; Wagiran, H. [Department of Physics, Universiti Teknologi Malaysia, 81310 Skudai, Johor Darul Takzim (Malaysia); Hossain, I., E-mail: imamhossain@utm.m [Department of Physics, Universiti Teknologi Malaysia, 81310 Skudai, Johor Darul Takzim (Malaysia); Ramli, A.T. [Department of Physics, Universiti Teknologi Malaysia, 81310 Skudai, Johor Darul Takzim (Malaysia); Bradley, D.A [Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); Hashim, S. [Department of Physics, Universiti Teknologi Malaysia, 81310 Skudai, Johor Darul Takzim (Malaysia); Ali, H. [Department of Radiotherapy and Oncology, Hospital Sultan Ismail, Johor Darul Takzim (Malaysia)

    2011-05-01

    This paper describes the thermoluminescence response, sensitivity, stability and reproducibility of SiO{sub 2} optical fibres with various electron energies and doses. The TL materials that comprise Al- and Ge-doped silica fibres were used in this experiment. The TL results are compared with those of the commercially available TLD-100. The doped SiO{sub 2} optical fibres and TLD-100 are placed in a solid phantom and irradiated with 6, 9 and 12 MeV electron beams at doses ranging from 0.2 to 4.0 Gy using the LINAC at Hospital Sultan Ismail, Johor Bahru, Malaysia. It was found that the commercially available Al- and Ge-doped optical fibres have a linear dose-TL signal relationship. The intensity of TL response of Ge-doped fibre is markedly greater than that of the Al-doped fibre.

  9. Measurement of Sub-Picosecond Electron Bunches via Electro-Optic Sampling of Coherent Transition Radiation

    Energy Technology Data Exchange (ETDEWEB)

    Maxwell, Timothy John [Northern Illinois U.

    2012-01-01

    Future collider applications as well as present high-gradient laser plasma wakefield accelerators and free-electron lasers operating with picosecond bunch durations place a higher demand on the time resolution of bunch distribution diagnostics. This demand has led to significant advancements in the field of electro-optic sampling over the past ten years. These methods allow the probing of diagnostic light such as coherent transition radiation or the bunch wakefields with sub-picosecond time resolution. We present results on the single-shot electro-optic spectral decoding of coherent transition radiation from bunches generated at the Fermilab A0 photoinjector laboratory. A longitudinal double-pulse modulation of the electron beam is also realized by transverse beam masking followed by a transverse-to-longitudinal phase-space exchange beamline. Live profile tuning is demonstrated by upstream beam focusing in conjunction with downstream monitoring of single-shot electro-optic spectral decoding of the coherent transition radiation.

  10. Electron irradiation response on Ge and Al-doped SiO 2 optical fibres

    Science.gov (United States)

    Yaakob, N. H.; Wagiran, H.; Hossain, I.; Ramli, A. T.; Bradley, D. A.; Hashim, S.; Ali, H.

    2011-05-01

    This paper describes the thermoluminescence response, sensitivity, stability and reproducibility of SiO 2 optical fibres with various electron energies and doses. The TL materials that comprise Al- and Ge-doped silica fibres were used in this experiment. The TL results are compared with those of the commercially available TLD-100. The doped SiO 2 optical fibres and TLD-100 are placed in a solid phantom and irradiated with 6, 9 and 12 MeV electron beams at doses ranging from 0.2 to 4.0 Gy using the LINAC at Hospital Sultan Ismail, Johor Bahru, Malaysia. It was found that the commercially available Al- and Ge-doped optical fibres have a linear dose-TL signal relationship. The intensity of TL response of Ge-doped fibre is markedly greater than that of the Al-doped fibre.

  11. Electron irradiation response on Ge and Al-doped SiO2 optical fibres

    International Nuclear Information System (INIS)

    Yaakob, N.H.; Wagiran, H.; Hossain, I.; Ramli, A.T.; Bradley, D.A; Hashim, S.; Ali, H.

    2011-01-01

    This paper describes the thermoluminescence response, sensitivity, stability and reproducibility of SiO 2 optical fibres with various electron energies and doses. The TL materials that comprise Al- and Ge-doped silica fibres were used in this experiment. The TL results are compared with those of the commercially available TLD-100. The doped SiO 2 optical fibres and TLD-100 are placed in a solid phantom and irradiated with 6, 9 and 12 MeV electron beams at doses ranging from 0.2 to 4.0 Gy using the LINAC at Hospital Sultan Ismail, Johor Bahru, Malaysia. It was found that the commercially available Al- and Ge-doped optical fibres have a linear dose-TL signal relationship. The intensity of TL response of Ge-doped fibre is markedly greater than that of the Al-doped fibre.

  12. Optical Sideband Generation: a Longitudinal Electron Beam Diagnostic Beyond the Laser Bandwidth Resolution Limit

    Energy Technology Data Exchange (ETDEWEB)

    Lawrence Berkeley National Laboratory; Tilborg, J. van; Matlis, N. H.; Plateau, G. R.; Leemans, W. P.

    2010-06-01

    Electro-optic sampling (EOS) is widely used as a technique to measure THz-domain electric field pulses such asthe self-fields of femtosecond electron beams. We present an EOS-based approach for single-shot spectral measurement that excels in simplicity (compatible with fiber integration) and bandwidth coverage (overcomes the laser bandwidth limitation), allowing few-fs electron beams or single-cycle THz pulses to be characterized with conventional picosecond probes. It is shown that the EOS-induced optical sidebands on the narrow-bandwidth optical probe are spectrally-shifted replicas of the THz pulse. An experimental demonstration on a 0-3 THz source is presented.

  13. Optical depth sectioning in the aberration-corrected scanning transmission and scanning confocal electron microscope

    International Nuclear Information System (INIS)

    Behan, G; Nellist, P D

    2008-01-01

    The use of spherical aberration correctors in the scanning transmission electron microscope (STEM) has the effect of reducing the depth of field of the microscope, making three-dimensional imaging of a specimen possible by optical sectioning. Depth resolution can be improved further by placing aberration correctors and lenses pre and post specimen to achieve an imaging mode known as scanning confocal electron microscopy (SCEM). We present the calculated incoherent point spread functions (PSF) and optical transfer functions (OTF) of a STEM and SCEM. The OTF for a STEM is shown to have a missing cone region which results in severe blurring along the optic axis, which can be especially severe for extended objects. We also present strategies for reconstruction of experimental data, such as three-dimensional deconvolution of the point spread function.

  14. Optical manipulation of electron spin in quantum dot systems

    Science.gov (United States)

    Villas-Boas, Jose; Ulloa, Sergio; Govorov, Alexander

    2006-03-01

    Self-assembled quantum dots (QDs) are of particular interest for fundamental physics because of their similarity with atoms. Coupling two of such dots and addressing them with polarized laser light pulses is perhaps even more interesting. In this paper we use a multi-exciton density matrix formalism to model the spin dynamics of a system with single or double layers of QDs. Our model includes the anisotropic electron-hole exchange in the dots, the presence of wetting layer states, and interdot tunneling [1]. Our results show that it is possible to switch the spin polarization of a single self-assembled quantum dot under elliptically polarized light by increasing the laser intensity. In the nonlinear mechanism described here, intense elliptically polarized light creates an effective exchange channel between the exciton spin states through biexciton states, as we demonstrate by numerical and analytical methods. We further show that the effect persists in realistic ensembles of dots, and we propose alternative ways to detect it. We also extend our study to a double layer of quantum dots, where we find a competition between Rabi frequency and tunneling oscillations. [1] J. M. Villas-Boas, S. E. Ulloa, and A. O. Govorov, Phys. Rev. Lett. 94, 057404 (2005); Phys. Rev. B 69, 125342 (2004).

  15. Optical diagnosis system for intense electron beam diode plasma

    International Nuclear Information System (INIS)

    Yang Jie; Shu Ting; Zhang Jun; Fan Yuwei; Yang Jianhua; Liu Lie; Yin Yi; Luo Ling

    2012-01-01

    A nanosecond time-resolved imaging platform for diode plasmas diagnostics has been constructed based on the pulsed electron beam accelerator and high speed framing camera (HSFC). The accelerator can provide an electrical pulse with voltages of 200-500 kV, rise-time (from 10% to 90% amplitude) of 25 ns and duration of 110 ns. The diode currents up to kA level can be extracted. The trigger signal for camera was picked up by a water-resistor voltage divider after the main switch of the accelerator, which could avoid the disadvantageous influence of the time jitter caused by the breakdown of the gas gaps. Then the sampled negative electrical pulse was converted into a transistor-transistor logic (TTL) signal (5 V) with rise time of about 1.5 ns and time jitter less than 1 ns via a processor. And this signal was taken as the synchronization time base. According to the working characteristics of the camera, the synchronization scheme relying mainly on electrical pulse delay method supplemented by light signal delay method was determined to make sure that the camera can work synchronously with the light production and transportation from the diode plasma within the time scale of nanosecond. Moreover, shielding and filtering methods were used to restrain the interference on the measurement system from the accelerator. Finally, time resolved 2-D framing images of the diode plasma were acquired. (authors)

  16. Continuous wave protocol for simultaneous polarization and optical detection of P1-center electron spin resonance

    Science.gov (United States)

    Kamp, E. J.; Carvajal, B.; Samarth, N.

    2018-01-01

    The ready optical detection and manipulation of bright nitrogen vacancy center spins in diamond plays a key role in contemporary quantum information science and quantum metrology. Other optically dark defects such as substitutional nitrogen atoms (`P1 centers') could also become potentially useful in this context if they could be as easily optically detected and manipulated. We develop a relatively straightforward continuous wave protocol that takes advantage of the dipolar coupling between nitrogen vacancy and P1 centers in type 1b diamond to detect and polarize the dark P1 spins. By combining mutual spin flip transitions with radio frequency driving, we demonstrate the simultaneous optical polarization and detection of the electron spin resonance of the P1 center. This technique should be applicable to detecting and manipulating a broad range of dark spin populations that couple to the nitrogen vacancy center via dipolar fields, allowing for quantum metrology using these spin populations.

  17. Cerenkov light spectrum in an optical fiber exposed to a photon or electron radiation therapy beam

    International Nuclear Information System (INIS)

    Lambert, Jamil; Yin Yongbai; McKenzie, David R.; Law, Sue; Suchowerska, Natalka

    2009-01-01

    A Cerenkov signal is generated when energetic charged particles enter the core of an optical fiber. The Cerenkov intensity can be large enough to interfere with signals transmitted through the fiber. We determine the spectrum of the Cerenkov background signal generated in a poly(methyl methacrylate) optical fiber exposed to photon and electron therapeutic beams from a linear accelerator. This spectral measurement is relevant to discrimination of the signal from the background, as in scintillation dosimetry using optical fiber readouts. We find that the spectrum is approximated by the theoretical curve after correction for the wavelength dependent attenuation of the fiber. The spectrum does not depend significantly on the angle between the radiation beam and the axis of the fiber optic but is dependent on the depth in water at which the fiber is exposed to the beam.

  18. Optical modeling of plasma-deposited ZnO films: Electron scattering at different length scales

    International Nuclear Information System (INIS)

    Knoops, Harm C. M.; Loo, Bas W. H. van de; Smit, Sjoerd; Ponomarev, Mikhail V.; Weber, Jan-Willem; Sharma, Kashish; Kessels, Wilhelmus M. M.; Creatore, Mariadriana

    2015-01-01

    In this work, an optical modeling study on electron scattering mechanisms in plasma-deposited ZnO layers is presented. Because various applications of ZnO films pose a limit on the electron carrier density due to its effect on the film transmittance, higher electron mobility values are generally preferred instead. Hence, insights into the electron scattering contributions affecting the carrier mobility are required. In optical models, the Drude oscillator is adopted to represent the free-electron contribution and the obtained optical mobility can be then correlated with the macroscopic material properties. However, the influence of scattering phenomena on the optical mobility depends on the considered range of photon energy. For example, the grain-boundary scattering is generally not probed by means of optical measurements and the ionized-impurity scattering contribution decreases toward higher photon energies. To understand this frequency dependence and quantify contributions from different scattering phenomena to the mobility, several case studies were analyzed in this work by means of spectroscopic ellipsometry and Fourier transform infrared (IR) spectroscopy. The obtained electrical parameters were compared to the results inferred by Hall measurements. For intrinsic ZnO (i-ZnO), the in-grain mobility was obtained by fitting reflection data with a normal Drude model in the IR range. For Al-doped ZnO (Al:ZnO), besides a normal Drude fit in the IR range, an Extended Drude fit in the UV-vis range could be used to obtain the in-grain mobility. Scattering mechanisms for a thickness series of Al:ZnO films were discerned using the more intuitive parameter “scattering frequency” instead of the parameter “mobility”. The interaction distance concept was introduced to give a physical interpretation to the frequency dependence of the scattering frequency. This physical interpretation furthermore allows the prediction of which Drude models can be used in a specific

  19. EGUN: An electron optics and gun design program

    International Nuclear Information System (INIS)

    Herrmannsfeldt, W.B.

    1988-10-01

    The name EGUN has become commonly associated with the program also known as the SLAC Electron Trajectory Program. This document is an updated version of SLAC-226, published in 1979. The program itself has had substantial upgrading since then, but only a few new features are of much concern to the user. Most of the improvements are internal and are intended to improve speed or accuracy. EGUN is designed to compute trajectories of charged particles in electrostatic and magnetostatic fields, including the effects of space charge and self-magnetic fields. Starting options include Child's Law conditions on cathodes of various shapes, as well as used specified initial conditions. Either rectangular or cylindrical symmetry may be used. In the new jargon, the program is a 2-1/2 dimension code meaning 2-D in all fields and 3-D in all particle motion. A Poisson's Equation Solver is used to find the electrostatic fields by using difference equations derived from the boundary conditions. Magnetic fields are to be specified externally, by the user, by using one of several methods including data from another program or arbitrary configurations of coils. This edition of the documentation also covers the program EGN87c, which is a recently developed version of EGUN designed to be used on the newer models of personal computers, small main frames, work stations, etc. The EGN87c program uses the programming language C which is very transportable so the program should operate on any system that supports C. Plotting routines for most common PC monitors are included, and the capability to make hard copy plots on dot-matrix printer-plotters is provided. 18 refs., 7 figs

  20. Electron beam position stabilization with a piezo-electric optical correction system

    CERN Document Server

    Averett, T; McKeown, R D; Pitt, M

    1999-01-01

    A piezo-electrically controlled optical correction system was successfully used to reduce the helicity-correlated pulse-to-pulse position differences of a laser spot to better than +-100 nm at a pulse rate of 600 Hz. Using a simple feedback algorithm, average position differences of DELTA x-bar=-3.5+-4.2 nm and DELTA y-bar=2.6+-6.6 nm were obtained over a 6 h period. This optical correction system was successfully used in the polarized electron source at the Bates Linear Accelerator Center to stabilize the position of the electron beam during the recent SAMPLE experiment. Because this experiment measures a parity violating signal at the 10 sup - sup 6 level, it is sensitive to systematic effects which are correlated with the helicity of the incident electrons. One potentially large systematic effect is the helicity-correlated motion of the incident electron beam. By using this optical correction system, electron beam position differences at the location of the experiment were routinely kept well below +-100 n...

  1. Electronic and Optical Properties of Aluminum Oxide Before and After Surface Reduction by Ar+ Bombardment

    Directory of Open Access Journals (Sweden)

    D. Tahir

    2014-08-01

    Full Text Available The electronic and optical properties of a-Al2O3 after induced by 3-keV Ar+ sputtering have been studied quantitatively by use of reflection electron energy loss spectroscopy (REELS spectra. The band gap values of a-Al2O3 was determined from the onset values of the energy loss spectrum to the background level of REELS spectra as a function of time Ar+ bombardment. The bandgap changes from 8.4 eV before sputtering to 6.2 eV after 4 minutes of sputtering.The optical properties of α-Al2O3 thin films have been determined by comparing the experimental cross section obtained from reflection electron energy loss spectroscopy with the theoretical inelastic scattering cross section, deduced from the simulated energy loss function (ELF by using QUEELS-ε(k-REELS software. The peak assignments are based on ELF and compared with reported data on the electronic structure of α-Al2O3 obtained using different techniques. The results demonstrate that the electronic and optical properties before and after surface reduction will provide further understanding in the fundamental properties of α-Al2O3 which will be useful in the design, modeling and analysis of devices applications performance.

  2. Observation of vacuum-enhanced electron spin resonance of optically levitated nanodiamonds

    Science.gov (United States)

    Li, Tongcang; Hoang, Thai; Ahn, Jonghoon; Bang, Jaehoon

    Electron spins of diamond nitrogen-vacancy (NV) centers are important quantum resources for nanoscale sensing and quantum information. Combining such NV spin systems with levitated optomechanical resonators will provide a hybrid quantum system for many novel applications. Here we optically levitate a nanodiamond and demonstrate electron spin control of its built-in NV centers in low vacuum. We observe that the strength of electron spin resonance (ESR) is enhanced when the air pressure is reduced. To better understand this novel system, we also investigate the effects of trap power and measure the absolute internal temperature of levitated nanodiamonds with ESR after calibration of the strain effect. Our results show that optical levitation of nanodiamonds in vacuum not only can improve the mechanical quality of its oscillation, but also enhance the ESR contrast, which pave the way towards a novel levitated spin-optomechanical system for studying macroscopic quantum mechanics. The results also indicate potential applications of NV centers in gas sensing.

  3. New trends in the optical and electronic applications of polymers containing transition-metal complexes.

    Science.gov (United States)

    Liu, Shu-Juan; Chen, Yang; Xu, Wen-Juan; Zhao, Qiang; Huang, Wei

    2012-04-13

    Polymers containing transition-metal complexes exhibit excellent optical and electronic properties, which are different from those of polymers with a pure organic skeleton and combine the advantages of both polymers and metal complexes. Hence, research about this class of polymers has attracted more and more interest in recent years. Up to now, a number of novel polymers containing transition-metal complexes have been exploited, and significant advances in their optical and electronic applications have been achieved. In this article, we summarize some new research trends in the applications of this important class of optoelectronic polymers, such as chemo/biosensors, electronic memory devices and photovoltaic devices. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Single-shot electro-optic experiments for electron bunch diagnostics at Tsinghua Accelerator Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Wei; Du, Yingchao; Yan, Lixin; Hua, Jianfei; Zhang, Zhen; Zhou, Zheng [Accelerator Laboratory, Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Key Laboratory of Particle and Radiation Imaging, Tsinghua University, Ministry of Education, Beijing 100084 (China); Huang, Wenhui, E-mail: huangwh@mail.tsinghua.edu.cn [Accelerator Laboratory, Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Key Laboratory of Particle and Radiation Imaging, Tsinghua University, Ministry of Education, Beijing 100084 (China); Tang, Chuanxiang [Accelerator Laboratory, Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Key Laboratory of Particle and Radiation Imaging, Tsinghua University, Ministry of Education, Beijing 100084 (China); Li, Ming [Institute of Applied Electronics, China Academy of Engineering Physics, Mianyang 621900 (China)

    2016-10-21

    The electro-optic (EO) technique detects the Coulomb electric field distribution of relativistic electron bunches to obtain the associated longitudinal profile. This diagnostic method allows the direct time-resolved single-shot measurement and thus the real-time monitoring of the bunch profile and beam arrival time in a non-destructive way with sub-picosecond temporal resolution. In this paper, we report the measurement of the longitudinal profile of an electron bunch through electro-optic spectral decoding detection, in which the bunch profile is encoded into the spectra of the linearly chirped laser pulse. The experimental setup and measurement results of a 40 MeV electron bunch are presented, with a temporal profile length of 527 fs rms (~1.24 ps FWHM) and a beam arrival time jitter of 471 fs rms. Temporal resolution and future experimental improvement are also discussed.

  5. Long-wavelength optical phonon behavior in uniaxial strained graphene: Role of electron-phonon interaction

    Science.gov (United States)

    Assili, M.; Haddad, S.

    2014-09-01

    We derive the frequency shifts and the broadening of Γ-point longitudinal optical (LO) and transverse optical (TO) phonon modes, due to electron-phonon interaction, in graphene under uniaxial strain as a function of the electron density and the disorder amount. We show that, in the absence of a shear strain component, such interaction gives rise to a lifting of the degeneracy of the LO and TO modes which contributes to the splitting of the G Raman band. The anisotropy of the electronic spectrum, induced by the strain, results in a polarization dependence of the LO and TO modes. This dependence is in agreement with the experimental results showing a periodic modulation of the Raman intensity of the split G peak. Moreover, the anomalous behavior of the frequency shift reported in undeformed graphene is found to be robust under strain.

  6. Localized second-order optical potential for electron scattering in terms of imaginary-frequency susceptibilities

    International Nuclear Information System (INIS)

    Valone, S.M.; Truhlar, D.G.; Thirumialai, D.

    1982-01-01

    A local approximation to the second-order optical potential for elastic scattering of low-energy electrons from ground-state atoms is expressed in terms of the imaginary-frequency susceptibilities of the atom due to a point charge and to modified perturbing potentials. This provides a basis for the physically appealing concept of regarding the perturbation due to the projectile as having a position-dependent effective frequency associated with it. The result is extended to higher energies with the use of the concept of a local kinetic energy. With a semiclassical approximation the result reduces to a simple general form that should be useful for model potential studies of electron-atom and electron-molecule scattering. Alternatively, variational functionals for the susceptibilities can be used to calculate the approximate optical potential most rigorously without making effective-frequency, average-kinetic-energy, or semiclassical approximations. Intermediate levels of rigor are also possible

  7. Electronic and Optical Properties of CuO Based on DFT+U and GW Approximation

    International Nuclear Information System (INIS)

    Ahmad, F; Agusta, M K; Dipojono, H K

    2016-01-01

    We report ab initio calculations of electronic structure and optical properties of monoclinic CuO based on DFT+U and GW approximation. CuO is an antiferromagnetic material with strong electron correlations. Our calculation shows that DFT+U and GW approximation sufficiently reliable to investigate the material properties of CuO. The calculated band gap of DFT+U for reasonable value of U slightly underestimates. The use of GW approximation requires adjustment of U value to get realistic result. Hybridization Cu 3dxz, 3dyz with O 2p plays an important role in the formation of band gap. The calculated optical properties based on DFT+U and GW corrections by solving Bethe-Salpeter are in good agreement with the calculated electronic properties and the experimental result. (paper)

  8. Old Star's "Rebirth" Gives Astronomers Surprises

    Science.gov (United States)

    2005-04-01

    Astronomers using the National Science Foundation's Very Large Array (VLA) radio telescope are taking advantage of a once-in-a-lifetime opportunity to watch an old star suddenly stir back into new activity after coming to the end of its normal life. Their surprising results have forced them to change their ideas of how such an old, white dwarf star can re-ignite its nuclear furnace for one final blast of energy. Sakurai's Object Radio/Optical Images of Sakurai's Object: Color image shows nebula ejected thousands of years ago. Contours indicate radio emission. Inset is Hubble Space Telescope image, with contours indicating radio emission; this inset shows just the central part of the region. CREDIT: Hajduk et al., NRAO/AUI/NSF, ESO, StSci, NASA Computer simulations had predicted a series of events that would follow such a re-ignition of fusion reactions, but the star didn't follow the script -- events moved 100 times more quickly than the simulations predicted. "We've now produced a new theoretical model of how this process works, and the VLA observations have provided the first evidence supporting our new model," said Albert Zijlstra, of the University of Manchester in the United Kingdom. Zijlstra and his colleagues presented their findings in the April 8 issue of the journal Science. The astronomers studied a star known as V4334 Sgr, in the constellation Sagittarius. It is better known as "Sakurai's Object," after Japanese amateur astronomer Yukio Sakurai, who discovered it on February 20, 1996, when it suddenly burst into new brightness. At first, astronomers thought the outburst was a common nova explosion, but further study showed that Sakurai's Object was anything but common. The star is an old white dwarf that had run out of hydrogen fuel for nuclear fusion reactions in its core. Astronomers believe that some such stars can undergo a final burst of fusion in a shell of helium that surrounds a core of heavier nuclei such as carbon and oxygen. However, the

  9. The production and extraction of polarized electrons from an optically pumped helium discharge

    International Nuclear Information System (INIS)

    Vandiver, R.J.; Schearer, L.D.; Gay, T.J.

    1992-01-01

    Polarized electrons are produced from interactions involving nearly 100% polarized helium 2 3 S 1 metastable atoms in a weak electrical discharge. The high metastable polarizations are obtained through the use of recently developed, high-power lasers tunable to the relevant helium transitions near 1083 nm and the development of a crossed beam pumping technique. The dominant interactions involving the 2 3 S 1 atoms and electrons are spin preserving; hence the electrons of the discharge attain a high polarization. The authors have extracted a well collimated electron beam with over 20 μA of current from the discharge. An optical polarimeter will be used to determine the polarization of the extracted electrons

  10. High definition in-situ electro-optical characterization for Roll to Roll printed electronics

    DEFF Research Database (Denmark)

    Pastorelli, Francesco

    2017-01-01

    Resume: Printed electronics is emerging as a new, large scale and cost effective technology that will be disruptive in fields such as energy harvesting, consumer electronics and medical sensors. The performance of printed organic electronic devices relies principally on the carrier mobility...... and molecular packing of the polymer semiconductor material. Unfortunately, the analysis of such materials is generally performed with destructive techniques, which are hard to make compatible with in situ measurements, and pose a great obstacle for the mass production of printed electronics devices. A rapid......-photon induced photoluminescence (TPPL) and second harmonic response. We anticipate that this non-linear optical method will substantially contribute to the understanding of printed electronic devices and demonstrate it as a promising novel tool for non-destructive and facile testing of materials during printing...

  11. Electron cyclotron emission from optically thin plasma in compact helical system

    International Nuclear Information System (INIS)

    Idei, Hiroshi; Kubo, Shin; Hosokawa, Minoru; Iguchi, Harukazu; Ohkubo, Kunizo; Sato, Teruyuki.

    1994-01-01

    A frequency spectrum of second harmonic electron cyclotron emission was observed for an optically thin plasma produced by fundamental electron cyclotron heating in a compact helical system. A radial electron temperature profile deduced from this spectrum neglecting the multiple reflections effect shows a clear difference from that measured by Thomson scattering. We relate the spectrum with the electron temperature profile by the modified emission model including the scrambling effect. The scrambling effect results from both mode conversion and change in the trajectory due to multiple reflections of the emitting ray at the vessel wall. The difference between the two temperature profiles is explained well by using the modified emission model. Reconstruction of the electron temperature profile from the spectrum using this model is also discussed. (author)

  12. Pupil size tracks perceptual content and surprise.

    Science.gov (United States)

    Kloosterman, Niels A; Meindertsma, Thomas; van Loon, Anouk M; Lamme, Victor A F; Bonneh, Yoram S; Donner, Tobias H

    2015-04-01

    Changes in pupil size at constant light levels reflect the activity of neuromodulatory brainstem centers that control global brain state. These endogenously driven pupil dynamics can be synchronized with cognitive acts. For example, the pupil dilates during the spontaneous switches of perception of a constant sensory input in bistable perceptual illusions. It is unknown whether this pupil dilation only indicates the occurrence of perceptual switches, or also their content. Here, we measured pupil diameter in human subjects reporting the subjective disappearance and re-appearance of a physically constant visual target surrounded by a moving pattern ('motion-induced blindness' illusion). We show that the pupil dilates during the perceptual switches in the illusion and a stimulus-evoked 'replay' of that illusion. Critically, the switch-related pupil dilation encodes perceptual content, with larger amplitude for disappearance than re-appearance. This difference in pupil response amplitude enables prediction of the type of report (disappearance vs. re-appearance) on individual switches (receiver-operating characteristic: 61%). The amplitude difference is independent of the relative durations of target-visible and target-invisible intervals and subjects' overt behavioral report of the perceptual switches. Further, we show that pupil dilation during the replay also scales with the level of surprise about the timing of switches, but there is no evidence for an interaction between the effects of surprise and perceptual content on the pupil response. Taken together, our results suggest that pupil-linked brain systems track both the content of, and surprise about, perceptual events. © 2015 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

  13. A surprising palmar nevus: A case report

    Directory of Open Access Journals (Sweden)

    Rana Rafiei

    2018-02-01

    Full Text Available Raised palmar or plantar nevus especially in white people is an unusual feature. We present an uncommon palmar compound nevus in a 26-year-old woman with a large diameter (6 mm which had a collaret-shaped margin. In histopathologic evaluation intralymphatic protrusions of nevic nests were noted. This case was surprising to us for these reasons: size, shape, location and histopathology of the lesion. Palmar nevi are usually junctional (flat and below 3 mm diameter and intra lymphatic protrusion or invasion in nevi is an extremely rare phenomenon.

  14. Transverse phase space mapping of relativistic electron beams using optical transition radiation

    Directory of Open Access Journals (Sweden)

    G. P. Le Sage

    1999-12-01

    Full Text Available Optical transition radiation (OTR has proven to be a versatile and effective diagnostic for measuring the profile, divergence, and emittance of relativistic electron beams with a wide range of parameters. Diagnosis of the divergence of modern high brightness beams is especially well suited to OTR interference (OTRI techniques, where multiple dielectric or metal foils are used to generate a spatially coherent interference pattern. Theoretical analysis of measured OTR and OTRI patterns allows precise measurement of electron beam emittance characteristics. Here we describe an extension of this technique to allow mapping of divergence characteristics as a function of transverse coordinates within a measured beam. We present the first experimental analysis of the transverse phase space of an electron beam using all optical techniques. Comparing an optically masked portion of the beam to the entire beam, we measure different angular spread and average direction of the particles. Direct measurement of the phase-space ellipse tilt angle has been demonstrated using this optical masking technique.

  15. Simulation of multicomponent light source for optical-electronic system of color analysis objects

    Science.gov (United States)

    Peretiagin, Vladimir S.; Alekhin, Artem A.; Korotaev, Valery V.

    2016-04-01

    Development of lighting technology has led to possibility of using LEDs in the specialized devices for outdoor, industrial (decorative and accent) and domestic lighting. In addition, LEDs and devices based on them are widely used for solving particular problems. For example, the LED devices are widely used for lighting of vegetables and fruit (for their sorting or growing), textile products (for the control of its quality), minerals (for their sorting), etc. Causes of active introduction LED technology in different systems, including optical-electronic devices and systems, are a large choice of emission color and LED structure, that defines the spatial, power, thermal and other parameters. Furthermore, multi-element and color devices of lighting with adjustable illumination properties can be designed and implemented by using LEDs. However, devices based on LEDs require more attention if you want to provide a certain nature of the energy or color distribution at all the work area (area of analysis or observation) or surface of the object. This paper is proposed a method of theoretical modeling of the lighting devices. The authors present the models of RGB multicomponent light source applied to optical-electronic system for the color analysis of mineral objects. The possibility of formation the uniform and homogeneous on energy and color illumination of the work area for this system is presented. Also authors showed how parameters and characteristics of optical radiation receiver (by optical-electronic system) affect on the energy, spatial, spectral and colorimetric properties of a multicomponent light source.

  16. Electronic and Optical Properties of Two-Dimensional GaN from First-Principles.

    Science.gov (United States)

    Sanders, Nocona; Bayerl, Dylan; Shi, Guangsha; Mengle, Kelsey A; Kioupakis, Emmanouil

    2017-12-13

    Gallium nitride (GaN) is an important commercial semiconductor for solid-state lighting applications. Atomically thin GaN, a recently synthesized two-dimensional material, is of particular interest because the extreme quantum confinement enables additional control of its light-emitting properties. We performed first-principles calculations based on density functional and many-body perturbation theory to investigate the electronic, optical, and excitonic properties of monolayer and bilayer two-dimensional (2D) GaN as a function of strain. Our results demonstrate that light emission from monolayer 2D GaN is blueshifted into the deep ultraviolet range, which is promising for sterilization and water-purification applications. Light emission from bilayer 2D GaN occurs at a similar wavelength to its bulk counterpart due to the cancellation of the effect of quantum confinement on the optical gap by the quantum-confined Stark shift. Polarized light emission at room temperature is possible via uniaxial in-plane strain, which is desirable for energy-efficient display applications. We compare the electronic and optical properties of freestanding two-dimensional GaN to atomically thin GaN wells embedded within AlN barriers in order to understand how the functional properties are influenced by the presence of barriers. Our results provide microscopic understanding of the electronic and optical characteristics of GaN at the few-layer regime.

  17. Controlling the optical field chaos in storage ring free-electron lasers

    International Nuclear Information System (INIS)

    Wang Wenjie

    1995-01-01

    The controlling of optical field chaos in a storage ring free-electron laser oscillator is discussed by using a phenomenal model. A novel method (which is called the 'beating method') of controlling chaos in a nonlinear dynamical system described by non-autonomous ordinary differential equations was developed. The result of theoretical analysis and numerical simulation shows that the optical field chaos in a storage ring free-electron laser oscillator can be suppressed and a periodic laser intensity can be obtained when a weak periodic control field is added to the optical cavity. The validity of this method of eliminating chaos is confirmed by the fact that the leading Lyapunov characteristic exponent of the system changes from a positive real number to a negative one. A further research is carried out, and it is found that only when the period of the control field equals to an integral multiple of that of the gain modulation in the optical cavity can the optical field chaos be suppressed. This means that the 'beating method' of controlling chaos is a kind of resonant method. A way to determine the 'best beating position' in the phase trajectory has also been obtained

  18. Electronic and optical properties of vacancy defects in single-layer transition metal dichalcogenides

    Science.gov (United States)

    Khan, M. A.; Erementchouk, Mikhail; Hendrickson, Joshua; Leuenberger, Michael N.

    2017-06-01

    A detailed first-principles study has been performed to evaluate the electronic and optical properties of single-layer (SL) transition metal dichalcogenides (TMDCs) (M X 2 ; M = transition metal such as Mo, W, and X = S, Se, Te), in the presence of vacancy defects (VDs). Defects usually play an important role in tailoring electronic, optical, and magnetic properties of semiconductors. We consider three types of VDs in SL TMDCs: (i) X vacancy, (ii) X2 vacancy, and (iii) M vacancy. We show that VDs lead to localized defect states (LDS) in the band structure, which in turn gives rise to sharp transitions in in-plane and out-of-plane optical susceptibilities, χ∥ and χ⊥. The effects of spin-orbit coupling (SOC) are also considered. We find that SOC splitting in LDS is directly related to the atomic number of the transition metal atoms. Apart from electronic and optical properties we also find magnetic signatures (local magnetic moment of ˜μB ) in MoSe2 in the presence of the Mo vacancy, which breaks the time-reversal symmetry and therefore lifts the Kramers degeneracy. We show that a simple qualitative tight-binding model (TBM), involving only the hopping between atoms surrounding the vacancy with an on-site SOC term, is sufficient to capture the essential features of LDS. In addition, the existence of the LDS can be understood from the solution of the two-dimensional Dirac Hamiltonian by employing infinite mass boundary conditions. In order to provide a clear description of the optical absorption spectra, we use group theory to derive the optical selection rules between LDS for both χ∥ and χ⊥.

  19. Projection-reduction method applied to deriving non-linear optical conductivity for an electron-impurity system

    Directory of Open Access Journals (Sweden)

    Nam Lyong Kang

    2013-07-01

    Full Text Available The projection-reduction method introduced by the present authors is known to give a validated theory for optical transitions in the systems of electrons interacting with phonons. In this work, using this method, we derive the linear and first order nonlinear optical conductivites for an electron-impurity system and examine whether the expressions faithfully satisfy the quantum mechanical philosophy, in the same way as for the electron-phonon systems. The result shows that the Fermi distribution function for electrons, energy denominators, and electron-impurity coupling factors are contained properly in organized manners along with absorption of photons for each electron transition process in the final expressions. Furthermore, the result is shown to be represented properly by schematic diagrams, as in the formulation of electron-phonon interaction. Therefore, in conclusion, we claim that this method can be applied in modeling optical transitions of electrons interacting with both impurities and phonons.

  20. Interpretation of the electron cyclotron emission of hot ASDEX upgrade plasmas at optically thin frequencies

    Energy Technology Data Exchange (ETDEWEB)

    Denk, Severin Sebastian; Stroth, Ulrich [Max-Planck-Institut fuer Plasmaphysik, D-85748 Garching (Germany); Physik-Department E28, Technische Universitaet Muenchen, 85748 Garching (Germany); Fischer, Rainer; Poli, Emanuele; Willensdorfer, Matthias; Maj, Omar; Stober, Joerg; Suttrop, Wolfgang [Max-Planck-Institut fuer Plasmaphysik, D-85748 Garching (Germany); Collaboration: The ASDEX Upgrade Team

    2016-07-01

    The electron cyclotron emission diagnostic (ECE) provides routinely electron temperature (T{sub e}) measurements. ''Kinetic effects'' (relativistic mass shift and Doppler shift) can cause the measured radiation temperatures (T{sub rad}) to differ from T{sub e} at cold resonance position complicating the determination of T{sub e} from the measured radiation temperature profile (T{sub rad}). For the interpretation of such ECE measurements an electron cyclotron forward model solving the radiation transport equation for given T{sub e} and electron density profiles is in use in the framework of Integrated Data Analysis at ASDEX Upgrade. While the original model lead to improved T{sub e} profiles near the plasma edge in moderately hot H-mode discharges, vacuum approximations in the model lead to inaccuracies given large T{sub e}. In hot plasmas ''wave-plasma interaction'', i.e. the dielectric effect of the background plasma onto the electron cyclotron emission, becomes important at optical thin measured frequencies. Additionally, given moderate electron densities and large T{sub e}, the refraction of the line of sight has to be considered for the interpretation of ECE measurements with low optical depth.

  1. Analysis of secondary electron emission for conducting materials using 4-grid LEED/AES optics

    International Nuclear Information System (INIS)

    Patino, M I; Wirz, R E; Raitses, Y; Koel, B E

    2015-01-01

    A facility utilizing 4-grid optics for LEED/AES (low energy electron diffraction/Auger electron spectroscopy) was developed to measure the total secondary electron yield and secondary electron energy distribution function for conducting materials. The facility and experimental procedure were validated with measurements of 50–500 eV primary electrons impacting graphite. The total yield was calculated from measurements of the secondary electron current (i) from the sample and (ii) from the collection assembly, by biasing each surface. Secondary electron yield results from both methods agreed well with each other and were within the spread of previous results for the total yield from graphite. Additionally, measurements of the energy distribution function of secondary electrons from graphite are provided for a wider range of incident electron energies. These results can be used in modeling plasma-wall interactions in plasmas bounded by graphite walls, such as are found in plasma thrusters, and divertors and limiters of magnetic fusion devices. (paper)

  2. Characterization and optimization of an optical and electronic architecture for photon counting

    Science.gov (United States)

    Correa, M. del M.; Pérez, F. R.

    2018-04-01

    This work shows a time-domain method for the discrimination and digitization of pulses coming from optical detectors, considering the presence of electronic noise and afterpulsing. The developed signal processing scheme is based on a time-to-digital converter (TDC) and a voltage discriminator. After setting appropriate parameters for taking spectra, acquisition data was corrected by wavelength, intensity response function, and noise suppression. The performance of this scheme is discussed by its characterization as well as the comparison of its spectra to those obtained by an Ocean Optics HR4000 commercial reference.

  3. The Electronic and Optical Properties of Au Doped Single-Layer Phosphorene

    Science.gov (United States)

    Zhu, Ziqing; Chen, Changpeng; Liu, Jiayi; Han, Lu

    2018-01-01

    The electronic properties and optical properties of single and double Au-doped phosphorene have been comparatively investigated using the first-principles plane-wave pseudopotential method based on density functional theory. The decrease from direct band gap 0.78 eV to indirect band gap 0.22 and 0.11 eV are observed in the single and double Au-doped phosphorene, respectively. The red shifts of absorbing edge occur in both doped systems, which consequently enhance the absorbing of infrared light in phosphorene. Band gap engineering can, therefore, be used to directly tune the optical absorption of phosphorene system by substitutional Au doping.

  4. Electronic properties and optical absorption of graphene-polyvinylidene fluoride nanocomposites: A theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, Siddheshwar, E-mail: schopra1@amity.edu

    2017-01-15

    Graphene/polyvinylidene fluoride (graphene/PVDF) nanocomposites were studied using Density functional theory (DFT)/Time dependent density functional theory (TDDFT) calculations. Five nanocomposite configurations were constructed. Electronic properties like binding energy, electronic gap and work function were calculated. The most stable structure was determined. The electronic gap of graphene shifts from semiconducting to conducting, on nanocomposite formation. Workfunction of the most stable nanocomposite was 4.34eV ± 0.05eV, close to that of the pristine graphene (4.33eV ± 0.05eV). Thermochemical analysis showed that the adsorption is spontaneous above ∼870 K, and endothermic in nature. TDDFT calculations were performed for B3LYP, LSDA, BHHLYP and PBE0 functionals. B3LYP and PBE0 are suitable in describing optical absorption. Optical gap of graphene shrinks, and light absorption gets enhanced on nanocomposite formation. - Highlights: • Various properties of graphene-PVDF nanocomposites were studied theoretically. • Electronic gap of graphene shifts to conducting nature, on composite formation. • Adsorption is spontaneous above ∼870 K, and endothermic in nature. • B3LYP and PBE0 functionals are suitable in describing absorption. • Optical absorption gets enhanced on nanocomposite formation.

  5. Electronic properties and optical absorption of graphene-polyvinylidene fluoride nanocomposites: A theoretical study

    International Nuclear Information System (INIS)

    Chopra, Siddheshwar

    2017-01-01

    Graphene/polyvinylidene fluoride (graphene/PVDF) nanocomposites were studied using Density functional theory (DFT)/Time dependent density functional theory (TDDFT) calculations. Five nanocomposite configurations were constructed. Electronic properties like binding energy, electronic gap and work function were calculated. The most stable structure was determined. The electronic gap of graphene shifts from semiconducting to conducting, on nanocomposite formation. Workfunction of the most stable nanocomposite was 4.34eV ± 0.05eV, close to that of the pristine graphene (4.33eV ± 0.05eV). Thermochemical analysis showed that the adsorption is spontaneous above ∼870 K, and endothermic in nature. TDDFT calculations were performed for B3LYP, LSDA, BHHLYP and PBE0 functionals. B3LYP and PBE0 are suitable in describing optical absorption. Optical gap of graphene shrinks, and light absorption gets enhanced on nanocomposite formation. - Highlights: • Various properties of graphene-PVDF nanocomposites were studied theoretically. • Electronic gap of graphene shifts to conducting nature, on composite formation. • Adsorption is spontaneous above ∼870 K, and endothermic in nature. • B3LYP and PBE0 functionals are suitable in describing absorption. • Optical absorption gets enhanced on nanocomposite formation.

  6. Electronic and optical properties of graphene-like InAs: An ab initio study

    Science.gov (United States)

    Sohrabi, Leila; Boochani, Arash; Ali Sebt, S.; Mohammad Elahi, S.

    2018-03-01

    The present work initially investigates structural, optical, and electronic properties of graphene-like InAs by using the full potential linear augmented plane wave method in the framework of density functional theory and is then compared with the bulk Indium Arsenide in the wurtzite phase. The lattice parameters are optimized with GGA-PBE and LDA approximations for both 2D- and 3D-InAs. In order to study the electronic properties of graphene-like InAs and bulk InAs in the wurtzite phase, the band gap is calculated by GGA-PBG and GGA-EV approximations. Moreover, optical parameters of graphene-like InAs and bulk InAs such as the real and imaginary parts of dielectric function, electron energy loss function, refractivity, extinction and absorption coefficients, and optical conductivity are investigated. Plasmonic frequencies of 2D- and 3D-InAs are also calculated by using maximum electron energy loss function and the roots of the real part of the dielectric function.

  7. Design and Analysis of an Electron Gun/Booster and Free Electron Laser Optical Theory

    Science.gov (United States)

    2010-09-01

    105 65. Stanford DC gun equipotentials . . . . . . . . . . . . . . . . . . . . . . 106 66. Energy plots for various electrode ratios...222 121. Graphical Cross-correlation Demonstration . . . . . . . . . . . . . . . . 223 122. 2D cross-correlation surface ...them enough energy to escape the metal’s surface . Once free of the metal, the electric field accelerates the electrons toward an anode. If the anode is

  8. Electronic, structural, and optical properties of host materials for inorganic phosphors

    International Nuclear Information System (INIS)

    Alemany, Pere; Moreira, Ibério de P.R.; Castillo, Rodrigo; Llanos, Jaime

    2012-01-01

    Highlights: ► We performed a first-principles DFT study of the electronic structures of several wide band gap insulators (La 2 O 3 , La 2 O 2 S, Y 2 O 3 Y 2 O 2 S, La 2 TeO 6 , and Y 2 TeO 6 ) used as host materials for inorganic phosphors. ► The electronic, structural, and optical properties calculated for these compounds are in good agreement with the available experimental data. ► The electronic structure of the M 2 TeO 6 phases exhibits distinct features that could allow a fine tuning of the optical properties of luminescent materials obtained by doping with rare earth metals. - Abstract: A family of large gap insulators used as host materials for inorganic phosphors (La 2 O 3 , La 2 O 2 S, Y 2 O 3 , Y 2 O 2 S, La 2 TeO 6 , and Y 2 TeO 6 ) have been studied by first-principles DFT based calculations. We have determined electronic, structural, and optical properties for all these compounds both at the LDA and GGA levels obtaining, in general, a good agreement with available experimental data and previous theoretical studies. The electronic structure for the M 2 TeO 6 phases, addressed in this work for the first time, reveals some significant differences with respect to the other compounds, especially in the region of the lower conduction band, where the appearance of a group of four isolated oxygen/tellurium based bands below the main part of the La (Y) centered conduction band is predicted to lead to significant changes in the optical properties of the two tellurium containing compounds with respect to the rest of compounds in the series.

  9. Doping of wide-bandgap titanium-dioxide nanotubes: optical, electronic and magnetic properties

    Science.gov (United States)

    Alivov, Yahya; Singh, Vivek; Ding, Yuchen; Cerkovnik, Logan Jerome; Nagpal, Prashant

    2014-08-01

    Doping semiconductors is an important step for their technological application. While doping bulk semiconductors can be easily achieved, incorporating dopants in semiconductor nanostructures has proven difficult. Here, we report a facile synthesis method for doping titanium-dioxide (TiO2) nanotubes that was enabled by a new electrochemical cell design. A variety of optical, electronic and magnetic dopants were incorporated into the hollow nanotubes, and from detailed studies it is shown that the doping level can be easily tuned from low to heavily-doped semiconductors. Using desired dopants - electronic (p- or n-doped), optical (ultraviolet bandgap to infrared absorption in co-doped nanotubes), and magnetic (from paramagnetic to ferromagnetic) properties can be tailored, and these technologically important nanotubes can be useful for a variety of applications in photovoltaics, display technologies, photocatalysis, and spintronic applications.Doping semiconductors is an important step for their technological application. While doping bulk semiconductors can be easily achieved, incorporating dopants in semiconductor nanostructures has proven difficult. Here, we report a facile synthesis method for doping titanium-dioxide (TiO2) nanotubes that was enabled by a new electrochemical cell design. A variety of optical, electronic and magnetic dopants were incorporated into the hollow nanotubes, and from detailed studies it is shown that the doping level can be easily tuned from low to heavily-doped semiconductors. Using desired dopants - electronic (p- or n-doped), optical (ultraviolet bandgap to infrared absorption in co-doped nanotubes), and magnetic (from paramagnetic to ferromagnetic) properties can be tailored, and these technologically important nanotubes can be useful for a variety of applications in photovoltaics, display technologies, photocatalysis, and spintronic applications. Electronic supplementary information (ESI) available: See DOI: 10.1039/c4nr02417f

  10. High-Resolution Two-Dimensional Optical Spectroscopy of Electron Spins

    Directory of Open Access Journals (Sweden)

    M. Salewski

    2017-08-01

    Full Text Available Multidimensional coherent optical spectroscopy is one of the most powerful tools for investigating complex quantum mechanical systems. While it was conceived decades ago in magnetic resonance spectroscopy using microwaves and radio waves, it has recently been extended into the visible and UV spectral range. However, resolving MHz energy splittings with ultrashort laser pulses still remains a challenge. Here, we analyze two-dimensional Fourier spectra for resonant optical excitation of resident electrons to localized trions or donor-bound excitons in semiconductor nanostructures subject to a transverse magnetic field. Particular attention is devoted to Raman coherence spectra, which allow one to accurately evaluate tiny splittings of the electron ground state and to determine the relaxation times in the electron spin ensemble. A stimulated steplike Raman process induced by a sequence of two laser pulses creates a coherent superposition of the ground-state doublet which can be retrieved only optically because of selective excitation of the same subensemble with a third pulse. This provides the unique opportunity to distinguish between different complexes that are closely spaced in energy in an ensemble. The related experimental demonstration is based on photon-echo measurements in an n-type CdTe/(Cd,MgTe quantum-well structure detected by a heterodyne technique. The difference in the sub-μeV range between the Zeeman splittings of donor-bound electrons and electrons localized at potential fluctuations can be resolved even though the homogeneous linewidth of the optical transitions is larger by 2 orders of magnitude.

  11. Electronic band-gap modified passive silicon optical modulator at telecommunications wavelengths.

    Science.gov (United States)

    Zhang, Rui; Yu, Haohai; Zhang, Huaijin; Liu, Xiangdong; Lu, Qingming; Wang, Jiyang

    2015-11-13

    The silicon optical modulator is considered to be the workhorse of a revolution in communications. In recent years, the capabilities of externally driven active silicon optical modulators have dramatically improved. Self-driven passive modulators, especially passive silicon modulators, possess advantages in compactness, integration, low-cost, etc. Constrained by a large indirect band-gap and sensitivity-related loss, the passive silicon optical modulator is scarce and has been not advancing, especially at telecommunications wavelengths. Here, a passive silicon optical modulator is fabricated by introducing an impurity band in the electronic band-gap, and its nonlinear optics and applications in the telecommunications-wavelength lasers are investigated. The saturable absorption properties at the wavelength of 1.55 μm was measured and indicates that the sample is quite sensitive to light intensity and has negligible absorption loss. With a passive silicon modulator, pulsed lasers were constructed at wavelengths at 1.34 and 1.42 μm. It is concluded that the sensitive self-driven passive silicon optical modulator is a viable candidate for photonics applications out to 2.5 μm.

  12. Novel optical waveguides by in-depth controlled electronic damage with swift ions

    Science.gov (United States)

    Olivares, J.; García-Navarro, A.; Méndez, A.; Agulló-López, F.; García, G.; García-Cabañes, A.; Carrascosa, M.

    2007-04-01

    We review recent results on a novel method to modify crystalline dielectric materials and fabricate optical waveguides and integrated optics devices. It relies on irradiation with medium-mass high-energy ions (2-50 MeV) where the electronic stopping power is dominant over that one associated to nuclear collisions. By exploiting the processing capabilities of the method, novel optical structures can be achieved at moderate (1014 cm-2) and even low and ultralow (1012 cm-2) fluences. In particular, step-like waveguides with a high index jump Δn ∼ 0.1-0.2, guiding both ordinary and extraordinary modes, have been prepared with F and O ions (20 MeV) at moderate fluences. They present good non-linear and electrooptic perfomance and low losses. (1 dB/cm). Moreover, useful optical waveguiding has been also achieved at ultralow frequencies (isolated track regime), using Cl and Si ions (40-45 MeV). In this latter case, the individual amorphous nanotracks, whose radius increases with depth, create an effective optical medium causing optical trapping.

  13. Novel optical waveguides by in-depth controlled electronic damage with swift ions

    International Nuclear Information System (INIS)

    Olivares, J.; Garcia-Navarro, A.; Mendez, A.; Agullo-Lopez, F.; Garcia, G.; Garcia-Cabanes, A.; Carrascosa, M.

    2007-01-01

    We review recent results on a novel method to modify crystalline dielectric materials and fabricate optical waveguides and integrated optics devices. It relies on irradiation with medium-mass high-energy ions (2-50 MeV) where the electronic stopping power is dominant over that one associated to nuclear collisions. By exploiting the processing capabilities of the method, novel optical structures can be achieved at moderate (10 14 cm -2 ) and even low and ultralow (10 12 cm -2 ) fluences. In particular, step-like waveguides with a high index jump Δn ∼ 0.1-0.2, guiding both ordinary and extraordinary modes, have been prepared with F and O ions (20 MeV) at moderate fluences. They present good non-linear and electrooptic perfomance and low losses. (1 dB/cm). Moreover, useful optical waveguiding has been also achieved at ultralow frequencies (isolated track regime), using Cl and Si ions (40-45 MeV). In this latter case, the individual amorphous nanotracks, whose radius increases with depth, create an effective optical medium causing optical trapping

  14. Elastic scattering by hot electrons and apparent lifetime of longitudinal optical phonons in gallium nitride

    Energy Technology Data Exchange (ETDEWEB)

    Khurgin, Jacob B., E-mail: jakek@jhu.edu [Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Bajaj, Sanyam; Rajan, Siddharth [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States)

    2015-12-28

    Longitudinal optical (LO) phonons in GaN generated in the channel of high electron mobility transistors (HEMT) are shown to undergo nearly elastic scattering via collisions with hot electrons. The net result of these collisions is the diffusion of LO phonons in the Brillouin zone causing reduction of phonon and electron temperatures. This previously unexplored diffusion mechanism explicates how an increase in electron density causes reduction of the apparent lifetime of LO phonons, obtained from the time resolved Raman studies and microwave noise measurements, while the actual decay rate of the LO phonons remains unaffected by the carrier density. Therefore, the saturation velocity in GaN HEMT steadily declines with increased carrier density, in a qualitative agreement with experimental results.

  15. Electron transport and nonlinear optical properties of substituted aryldimesityl boranes: a DFT study.

    Directory of Open Access Journals (Sweden)

    Altaf Hussain Pandith

    Full Text Available A comprehensive theoretical study was carried out on a series of aryldimesityl borane (DMB derivatives using Density Functional theory. Optimized geometries and electronic parameters like electron affinity, reorganization energy, frontiers molecular contours, polarizability and hyperpolarizability have been calculated by employing B3PW91/6-311++G (d, p level of theory. Our results show that the Hammett function and geometrical parameters correlates well with the reorganization energies and hyperpolarizability for the series of DMB derivatives studied in this work. The orbital energy study reveals that the electron releasing substituents increase the LUMO energies and electron withdrawing substituents decrease the LUMO energies, reflecting the electron transport character of aryldimesityl borane derivatives. From frontier molecular orbitals diagram it is evident that mesityl rings act as the donor, while the phenylene and Boron atom appear as acceptors in these systems. The calculated hyperpolarizability of secondary amine derivative of DMB is 40 times higher than DMB (1. The electronic excitation contributions to the hyperpolarizability studied by using TDDFT calculation shows that hyperpolarizability correlates well with dipole moment in ground and excited state and excitation energy in terms of the two-level model. Thus the results of these calculations can be helpful in designing the DMB derivatives for efficient electron transport and nonlinear optical material by appropriate substitution with electron releasing or withdrawing substituents on phenyl ring of DMB system.

  16. Morphology, optical and ionic conductivity studies of electron beam irradiated polymer electrolyte film

    Science.gov (United States)

    Devendrappa, H.; Yesappa, L.; Niranjana, M.; Ashokkumar, S. P.; Vijeth, H.; Ganesh, S.

    2018-04-01

    The effects of electron beam (EB) irradiation on morphology, optical properties and ionic conductivity of (PVdF-co-HFP: LiClO4=90:10, PHL10) electrolyte films. The FESEM image reveal increasing porous morphology with increasing EB dose confirms the polymer degradation as result more amorphousity. The optical absorbance was found to be increase with red shift in UV region and direct optical band gaps was found decreased upon EB dose from 3.70 eV to 2.65 eV. The ionic conductivity increases slowly in lower frequency, whereas rapidly increases at the high frequency and found about 8.28×10-4 S/cm at 120 kGy dose. The obtained results suggest that the physical properties of polymer electrolytes can be changed using EB irradiation as requirement.

  17. Magnetic, electronic, dielectric and optical properties of Pr(Ca:Sr)MnO 3

    Science.gov (United States)

    Sichelschmidt, J.; Paraskevopoulos, M.; Brando, M.; Wehn, R.; Ivannikov, D.; Mayr, F.; Pucher, K.; Hemberger, J.; Pimenov, A.; Krug von Nidda, H.-A.; Lunkenheimer, P.; Ivanov, V. Yu.; Mukhin, A. A.; Balbashov, A. M.; Loidl, A.

    2001-03-01

    The charge-ordered perovskite Pr0.65Ca0.28Sr0.07MnO3 was investigated by means of magnetic susceptibility, specific heat, dielectric and optical spectroscopy and electron-spin resonance techniques. Under moderate magnetic fields, the charge order melts yielding colossal magnetoresistance effects with changes of the resistivity over eleven orders of magnitude. The optical conductivity is studied from audio frequencies far into the visible spectral regime. Below the phonon modes hopping conductivity is detected. Beyond the phonon modes the optical conductivity is explained by polaronic excitations out of a bound state. ESR techniques yield detailed informations on the (H,T ) phase diagram and reveal a broadening of the linewidth which can be modeled in terms of activated polaron hopping.

  18. Electronic and Optical Properties of TiS_2 Determined from Generalized Gradient Approximation Study

    International Nuclear Information System (INIS)

    El-Kouch, Hamza; Farh, Larbi El; Sayah, Jamal; Challioui, Allal

    2015-01-01

    The electronic and optical properties of TiS_2 are studied by using an ab-initio calculation within the frame of density functional theory. A linearized and augmented plane wave basis set with the generalized gradient approximation as proposed by Perdew et al. is used for the energy exchange-correlation determination. The results show a metallic character of TiS_2, and the plots of total and partial densities of states of TiS_2 show the metallic character of the bonds and a strong hybridization between the states d of Ti and p of S below the Fermi energy. The optical properties of the material such as real and imaginary parts of dielectric constant (ϵ(ω) = ϵ_1(ω) + iϵ_2(ω)), refractive index n(ω), optical reflectivity R(ω), for E//x and E//z are performed for the energy range of 0–14 eV. (paper)

  19. Real-time data acquisition and computation for the SSC using optical and electronic technologies

    International Nuclear Information System (INIS)

    Cantrell, C.D.; Fenyves, E.J.; Wallace, B.

    1990-01-01

    The authors discuss combinations of optical and electronic technologies that may be able to address major data-filtering and data-analysis problems at the SSC. Novel scintillation detectors and optical readout may permit the use of optical processing techniques for trigger decisions and particle tracking. Very-high-speed fiberoptic local-area networks will be necessary to pipeline data from the detectors to the triggers and from the triggers to computers. High-speed, few-processor MIMD superconductors with advanced fiberoptic I/O technology offer a usable, cost-effective alternative to the microprocessor farms currently proposed for event selection and analysis for the SSC. The use of a real-time operating system that provides standard programming tools will facilitate all tasks, from reprogramming the detectors' event-selection criteria to detector simulation and event analysis. 34 refs., 1 fig., 1 tab

  20. Electronic and optical properties of phosphorene-like arsenic phosphorus: a many-body study

    Science.gov (United States)

    Shu, Huabing; Guo, Jiyuan

    2018-03-01

    By employing density functional and many-body perturbation theories, we explore the geometrics, quasiparticle band structure, and optical response of two-dimensional arsenic phosphorus (α-AsxP1-x). Calculations indicate that the α-AsxP1-x exhibits excellent stability at high temperature. The quasi-particle bandgap of α-AsxP1-x is highly tunable in a broad range of 1.54-2.14 eV depending on the composition. The optical absorption of α-AsxP1-x can cover the visible and ultraviolet regions, and is highly anisotropic. More interestingly, it is tunable to optical absorption of α-AsxP1-x when the composition continuously increased. Also, they have sizable exciton binding energies. These findings suggest that α-AsxP1-x holds great potentials for applications in high-performance electronics and optoelectronics.

  1. Primary Care Practice: Uncertainty and Surprise

    Science.gov (United States)

    Crabtree, Benjamin F.

    I will focus my comments on uncertainty and surprise in primary care practices. I am a medical anthropologist by training, and have been a full-time researcher in family medicine for close to twenty years. In this talk I want to look at primary care practices as complex systems, particularly taking the perspective of translating evidence into practice. I am going to discuss briefly the challenges we have in primary care, and in medicine in general, of translating new evidence into the everyday care of patients. To do this, I will look at two studies that we have conducted on family practices, then think about how practices can be best characterized as complex adaptive systems. Finally, I will focus on the implications of this portrayal for disseminating new knowledge into practice.

  2. Surprises and counterexamples in real function theory

    CERN Document Server

    Rajwade, A R

    2007-01-01

    This book presents a variety of intriguing, surprising and appealing topics and nonroutine theorems in real function theory. It is a reference book to which one can turn for finding that arise while studying or teaching analysis.Chapter 1 is an introduction to algebraic, irrational and transcendental numbers and contains the Cantor ternary set. Chapter 2 contains functions with extraordinary properties; functions that are continuous at each point but differentiable at no point. Chapters 4 and intermediate value property, periodic functions, Rolle's theorem, Taylor's theorem, points of tangents. Chapter 6 discusses sequences and series. It includes the restricted harmonic series, of alternating harmonic series and some number theoretic aspects. In Chapter 7, the infinite peculiar range of convergence is studied. Appendix I deal with some specialized topics. Exercises at the end of chapters and their solutions are provided in Appendix II.This book will be useful for students and teachers alike.

  3. Using optically stimulated electrons from quartz for the estimation of natural doses

    DEFF Research Database (Denmark)

    Ankjærgaard, Christina; Murray, A.S.; Denby, Phil M.

    2009-01-01

    A flow-through Geiger-Müller pancake electron detector attachment has been fitted to a standard Risø TL/OSL reader enabling optically stimulated electrons (OSE) to be measured simultaneously with optically stimulated luminescence (OSL). Using this detector, OSE and OSL measurements from natural......, a dose recovery test shows that OSE can successfully recover a laboratory dose of 300 Gy given before any laboratory thermal treatment, for preheating temperatures between 160 and 260 °C. Furthermore, for the first time natural OSE decay curves are detected and these signals are used to estimate a burial...... dose using the single-aliquot regenerative-dose (SAR) procedure. Finally, a comparative study of the equivalent doses estimated using both OSE and OSL from 10 quartz samples are presented, and it is shown that OSE has a significant potential in retrospective dosimetry....

  4. Electronic and optical properties of new multifunctional materials via half-substituted hematite: First principles calculations

    KAUST Repository

    Yang, Hua

    2012-01-01

    Electronic structure and optical properties of α-FeMO 3 systems (M = Sc, Ti, V, Cr, Cu, Cd or In) have been investigated using first principles calculations. All of the FeMO 3 systems have a large net magnetic moment. The ground state of pure α-Fe 2O 3 is an antiferromagnetic insulator. For M = Cu or Cd, the systems are half-metallic. Strong absorption in the visible region can be observed in the Cu and Cd-doped systems. Systems with M = Sc, Ti, V, Cr or In are not half-metallic and are insulators. The strongest peaks shift toward shorter wavelengths in the absorption spectra. It is concluded that transition metal doping can modify the electronic structure and optical properties of α-FeMO 3 systems. This journal is © 2012 The Royal Society of Chemistry.

  5. Electronic structure and optical absorption spectra of Y2 and Zr2 dimers

    International Nuclear Information System (INIS)

    Gutsev, G.L.

    1989-01-01

    The electron structure, ionization potentials from valent levels and energies of optic transitions of Y 2 and Zr 2 dimers are calculated within the framework of discrete-variatin X α -method. It is shown that the symmetry state 1 Σ g + is the main state of Y 2 and Zr 2 dimers, and the atoms in dimers have high-spin 4d n+1 5s 1 configuration. The chemical binding in Y 2 has the dominating 5s-5s nature which is revealed in a considerable interatomic distance; binding of 4d-electrons brings about a significant decrease in the bond length in Zr 2 dimer. The theoretical spectrum of optical absorption of Zr 2 agrees well with the obtained experimental spectrum of this molecule isolated in the organ matrix

  6. Study on time of flight property of electron optical systems by differential algebraic method

    International Nuclear Information System (INIS)

    Cheng Min; Tang Tiantong; Yao Zhenhua

    2002-01-01

    Differential algebraic method is a powerful and promising technique in computer numerical analysis. When applied to nonlinear dynamics systems, the arbitrary high-order transfer properties of the systems can be computed directly with high precision. In this paper, the principle of differential algebra is applied to study on the time of flight (TOF) property of electron optical systems and their arbitrary order TOF transfer properties can be numerically calculated out. As an example, TOF transfer properties of a uniform magnetic sector field analyzer have been studied by differential algebraic method. Relative errors of the first-order and second-order TOF transfer coefficients of the magnetic sector field analyzer are of the order 10 -11 or smaller compared with the analytic solutions. It is proved that differential algebraic TOF method is of high accuracy and very helpful for high-order TOF transfer property analysis of electron optical systems. (author)

  7. Optical transition radiation measurements for the Los Alamos and Boeing Free-Electron Laser experiments

    Energy Technology Data Exchange (ETDEWEB)

    Lumpkin, A.H.; Feldman, R.B.; Feldman, D.W.; Apgar, S.A.; Calsten, B.E.; Fiorito, R.B.; Rule, D.W.

    1988-01-01

    Optical transition radiation (OTR) measurements of the electron-beam emittance have been performed at a location just before the wiggler in the Los Alamos Free-Electron Laser (FEL) experiment. Beam profiles and beam divergence patterns from a single macropulse were recorded simultaneously using two intensified charge-injection device (CID) television cameras and an optical beamsplitter. Both single-foil OTR and two-foil OTR interference experiments were performed. Preliminary results are compared to a reference variable quadrupole, single screen technique. New aspects of using OTR properties for pointing the e-beam on the FEL oscillator axis, as well as measuring e-beam emittance are addressed. 7 refs., 9 figs.

  8. Optical-electronic shape recognition system based on synergetic associative memory

    Science.gov (United States)

    Gao, Jun; Bao, Jie; Chen, Dingguo; Yang, Youqing; Yang, Xuedong

    2001-04-01

    This paper presents a novel optical-electronic shape recognition system based on synergetic associative memory. Our shape recognition system is composed of two parts: the first one is feature extraction system; the second is synergetic pattern recognition system. Hough transform is proposed for feature extraction of unrecognized object, with the effects of reducing dimensions and filtering for object distortion and noise, synergetic neural network is proposed for realizing associative memory in order to eliminate spurious states. Then we adopt an approach of optical- electronic realization to our system that can satisfy the demands of real time, high speed and parallelism. In order to realize fast algorithm, we replace the dynamic evolution circuit with adjudge circuit according to the relationship between attention parameters and order parameters, then implement the recognition of some simple images and its validity is proved.

  9. Alignment of Duke free electron laser storage ring and optical beam delivery system

    International Nuclear Information System (INIS)

    Emamian, M.; Hower, N.

    1999-01-01

    Duke Free Electron Laser Laboratory (DFELL) hosts a 1.1 GeV electron beam storage ring facility which is capable of generating beams in the range of nearly monochromatic gamma rays to high peak power infra red (IR) laser. In this report specifications and procedures for alignment of OK-4 /Duke storage ring FEL wiggler and optical cavity mirrors will be discussed. The OK-4 FEL lasing has demonstrated a series of world record in the last few years. In August of this year the OK-4 FEL successfully commissioned to laser at 193.7 nm. Also in this article, alignment of the γ-ray and UV optical beam delivery system that is currently in progress will be described. (authors)

  10. A correlative optical microscopy and scanning electron microscopy approach to locating nanoparticles in brain tumors.

    Science.gov (United States)

    Kempen, Paul J; Kircher, Moritz F; de la Zerda, Adam; Zavaleta, Cristina L; Jokerst, Jesse V; Mellinghoff, Ingo K; Gambhir, Sanjiv S; Sinclair, Robert

    2015-01-01

    The growing use of nanoparticles in biomedical applications, including cancer diagnosis and treatment, demands the capability to exactly locate them within complex biological systems. In this work a correlative optical and scanning electron microscopy technique was developed to locate and observe multi-modal gold core nanoparticle accumulation in brain tumor models. Entire brain sections from mice containing orthotopic brain tumors injected intravenously with nanoparticles were imaged using both optical microscopy to identify the brain tumor, and scanning electron microscopy to identify the individual nanoparticles. Gold-based nanoparticles were readily identified in the scanning electron microscope using backscattered electron imaging as bright spots against a darker background. This information was then correlated to determine the exact location of the nanoparticles within the brain tissue. The nanoparticles were located only in areas that contained tumor cells, and not in the surrounding healthy brain tissue. This correlative technique provides a powerful method to relate the macro- and micro-scale features visible in light microscopy with the nanoscale features resolvable in scanning electron microscopy. Copyright © 2014 Elsevier Ltd. All rights reserved.

  11. Electronic and optical properties of AgAlO{sub 2}: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Bhamu, K.C., E-mail: kcbhamu85@gmail.com; Priolkar, K.R.

    2017-04-01

    In this paper, we present electronic and optical properties of silver-based delafossite compound AgAlO{sub 2} (AAO). For the electronic properties, we have computed band structure and density of states. The origin of band structure is elucidated in terms of density of states. A significant contribution in band structure comes from Ag-4d and O-2p states around the Fermi level. The estimated band gap shows the indirect semiconducting nature of AAO having the band gap value of 2.34 eV. For the optical properties, we have calculated frequency dependent dielectric functions. The peaks in the imaginary component of dielectric function are explained by electronic transitions in the dispersion relation. Our computed results are in agreement with those available in the literature. The wide band gap and hence transparency for the UV and visible incident light photons makes AAO a precious material for transparent electronics. - Highlights: • Applied different-different types of exchange-correlations and potentials. • Becke–Johnson with Hubbard potential (BJ + U) is better for 2H-AgAlO{sub 2}. • Band gap is in reasonable agreement with experimentally reported. • Origin of energy bands is elucidated in terms of density of states. • 2H-AgAlO{sub 2} is a promising candidate for transparent electronics.

  12. Electronic and optical properties of AgAlO_2: A first-principles study

    International Nuclear Information System (INIS)

    Bhamu, K.C.; Priolkar, K.R.

    2017-01-01

    In this paper, we present electronic and optical properties of silver-based delafossite compound AgAlO_2 (AAO). For the electronic properties, we have computed band structure and density of states. The origin of band structure is elucidated in terms of density of states. A significant contribution in band structure comes from Ag-4d and O-2p states around the Fermi level. The estimated band gap shows the indirect semiconducting nature of AAO having the band gap value of 2.34 eV. For the optical properties, we have calculated frequency dependent dielectric functions. The peaks in the imaginary component of dielectric function are explained by electronic transitions in the dispersion relation. Our computed results are in agreement with those available in the literature. The wide band gap and hence transparency for the UV and visible incident light photons makes AAO a precious material for transparent electronics. - Highlights: • Applied different-different types of exchange-correlations and potentials. • Becke–Johnson with Hubbard potential (BJ + U) is better for 2H-AgAlO_2. • Band gap is in reasonable agreement with experimentally reported. • Origin of energy bands is elucidated in terms of density of states. • 2H-AgAlO_2 is a promising candidate for transparent electronics.

  13. All-optical time-resolved measurement of laser energy modulation in a relativistic electron beam

    Directory of Open Access Journals (Sweden)

    D. Xiang

    2011-11-01

    Full Text Available We propose and demonstrate an all-optical method to measure laser energy modulation in a relativistic electron beam. In this scheme the time-dependent energy modulation generated from the electron-laser interaction in an undulator is converted into time-dependent density modulation with a chicane, which is measured to infer the laser energy modulation. The method, in principle, is capable of simultaneously providing information on femtosecond time scale and 10^{-5} energy scale not accessible with conventional methods. We anticipate that this method may have wide applications in many laser-based advanced beam manipulation techniques.

  14. Electronic Structure and Optical Properties of Co and Fe doped ZnO

    Directory of Open Access Journals (Sweden)

    Li Chunping

    2016-01-01

    Full Text Available First-principle ultrasoft pseudo potential approach of the plane wave based on density functional theory has been used for studying the electronic characterization and optical properties of ZnO and Fe, Co doped ZnO. The results show that the doping impurities change the lattice parameters a little, but bring more changes in the electronic structures. The band gaps are broadened by doping. And the Fermi level accesses to the conduction band which will lead the system to show the character of metallic properties. The dielectric function and absorption peaks are identified and the changes compared to pure ZnO are analyzed in detail.

  15. Increased-accuracy numerical modeling of electron-optical systems with space-charge

    International Nuclear Information System (INIS)

    Sveshnikov, V.

    2011-01-01

    This paper presents a method for improving the accuracy of space-charge computation for electron-optical systems. The method proposes to divide the computational region into two parts: a near-cathode region in which analytical solutions are used and a basic one in which numerical methods compute the field distribution and trace electron ray paths. A numerical method is used for calculating the potential along the interface, which involves solving a non-linear equation. Preliminary results illustrating the improvement of accuracy and the convergence of the method for a simple test example are presented.

  16. Photoabsorption Spectrum and Optically Forbidden Transitions of Krypton by Electron Impact

    Institute of Scientific and Technical Information of China (English)

    苑震生; 朱林繁; 李文斌; 成华东; 徐克尊

    2002-01-01

    A high resolution fast electron energy loss spectrometer with multi-channel energy analysis was employed. The maxima just above the threshold 4p-1(2P1/2), which is regarded as a shape resonance, was obtained at 16.3 eV. The optically forbidden excitations of 4s electron were measured for the first time, and the energy positions are 23.75 eV(4s-15s), 25.66 eV (4s-16s/4d) and 26.60 eV(4s-17s/5d).

  17. Electronic, magnetic and optical properties of B, C, N and F doped MgO monolayer

    Science.gov (United States)

    Moghadam, A. Dashti; Maskane, P.; Esfandiari, S.

    2018-06-01

    MgO as one of the alkaline earth oxides has various applications in industry. In this work, we aim to investigate the electronic, optical and magnetic properties of MgO monolayers. Furthermore, monolayer structures with substituted B, N, C and F atoms instead of O atom are studied. These results indicate that MgO layer has possessed potential application in optoelectronic and spintronic nano-devices.

  18. The measurement of the optical cavity length for the infrared free electron laser

    International Nuclear Information System (INIS)

    Curtis, C.J.; Dahlberg, J.C.; Oren, W.A.; Tremblay, K.J.

    1999-01-01

    One of the final tasks involved in the alignment of the newly constructed Free Electron Laser at the Thomas Jefferson National Accelerator Facility was to accurately measure the length between two mirrors which make up the optical cavity. This presentation examines the survey techniques and equipment assembled in order to complete these measurements, together with the possible sources of error, and the accuracy achieved. (authors)

  19. Electron accelerator with a laser ignition for investigation of beam plasma by optical methods

    International Nuclear Information System (INIS)

    Kabanov, S.N.; Korolev, A.A.; Kul'beda, V.E.; Razumovskij, A.I.; Trukhin, V.A.

    1990-01-01

    Facility to conduct investigations into dense gas beam plasma is described. Facility comprises: electron accelerator (200-300 keV, 5kA, 20ns), OGM-40 ignition ruby laser LZhI-501 diagnostic laser (with 0.55-0.66 μm tunable wave length), Michelson interferometer and diagnostic equipment for optical measurements. Laser ignition of spark gap is introduced to strong synchronization (±10ns) of radiation pulse of diagnostic laser with beam current pulse

  20. Improved rate control for electron-beam evaporation and evaluation of optical performance improvements.

    Science.gov (United States)

    Gevelber, Michael; Xu, Bing; Smith, Douglas

    2006-03-01

    A new deposition-rate-control and electron-beam-gun (e-gun) strategy was developed that significantly reduces the growth-rate variations for e-beam-deposited SiO2 coatings. The resulting improvements in optical performance are evaluated for multilayer bandpass filters. The adverse effect of uneven silica-source depletion on coating spectral performances during long deposition runs is discussed.

  1. Electron and nuclear spin interactions in the optical spectra of single GaAs quantum dots.

    Science.gov (United States)

    Gammon, D; Efros, A L; Kennedy, T A; Rosen, M; Katzer, D S; Park, D; Brown, S W; Korenev, V L; Merkulov, I A

    2001-05-28

    Fine and hyperfine splittings arising from electron, hole, and nuclear spin interactions in the magneto-optical spectra of individual localized excitons are studied. We explain the magnetic field dependence of the energy splitting through competition between Zeeman, exchange, and hyperfine interactions. An unexpectedly small hyperfine contribution to the splitting close to zero applied field is described well by the interplay between fluctuations of the hyperfine field experienced by the nuclear spin and nuclear dipole/dipole interactions.

  2. Elementary and advanced Lie algebraic methods with applications to accelerator design, electron microscopes, and light optics

    International Nuclear Information System (INIS)

    Dragt, A.J.

    1987-01-01

    A review is given of elementary Lie algebraic methods for treating Hamiltonian systems. This review is followed by a brief exposition of advanced Lie algebraic methods including resonance bases and conjugacy theorems. Finally, applications are made to the design of third-order achromats for use in accelerators, to the design of subangstroem resolution electron microscopes, and to the classification and study of high order aberrations in light optics. (orig.)

  3. Use of thin films obtained by electron beam evaporation as optical wave guide

    International Nuclear Information System (INIS)

    Nobre, S.A.A.; Oliveira, C.A.S. de; Freire, G.F.de O.

    1986-01-01

    Thin films evaporated by electron beam for the fabrication of planar optical waveguides were used. The tested materials were aluminium oxide (Al 2 O 3 ) and tantalum pentoxide (Ta 2 O 5 ). The effect of annealing conditions on the film absorption was investigated for Ta 2 O 5 . The Al 2 O 3 films were characterized by the method of guided modes, in terms of refractive index measurements and film thickness. Atenuation measurements were also carried out. (M.C.K.) [pt

  4. Tunable electronic, electrical and optical properties of graphene oxide sheets by ion irradiation

    Science.gov (United States)

    Jayalakshmi, G.; Saravanan, K.; Panigrahi, B. K.; Sundaravel, B.; Gupta, Mukul

    2018-05-01

    The tunable electronic, electrical and optical properties of graphene oxide (GO) sheets were investigated using a controlled reduction by 500 keV Ar+-ion irradiation. The carbon to oxygen ratio of the GO sheets upon the ion beam reduction has been estimated using resonant Rutherford backscattering spectrometry analyses and its effect on the electrical and optical properties of GO sheets has been studied using sheet resistance measurements and photoluminescence (PL) measurements. The restoration of sp 2-hybridized carbon atoms within the sp 3 matrix is found to be increases with increasing the Ar+-ion fluences as evident from Fourier transform infrared, and x-ray absorption near-edge structure measurements. The decrease in the number of disorder-induced local density of states (LDOSs) within the π-π* gap upon the reduction causes the shifting of PL emission from near infra-red to blue region and decreases the sheet resistance. The improved electrical and optical properties of GO sheets were correlated to the decrease in the number of LDOSs within the π-π* gap. Our experimental investigations suggest ion beam irradiation is one of an effective approaches to reduce GO to RGO and to tailor its electronic, electrical and optical properties.

  5. Superluminescence from an optically pumped molecular tunneling junction by injection of plasmon induced hot electrons

    Directory of Open Access Journals (Sweden)

    Kai Braun

    2015-05-01

    Full Text Available Here, we demonstrate a bias-driven superluminescent point light-source based on an optically pumped molecular junction (gold substrate/self-assembled molecular monolayer/gold tip of a scanning tunneling microscope, operating at ambient conditions and providing almost three orders of magnitude higher electron-to-photon conversion efficiency than electroluminescence induced by inelastic tunneling without optical pumping. A positive, steadily increasing bias voltage induces a step-like rise of the Stokes shifted optical signal emitted from the junction. This emission is strongly attenuated by reversing the applied bias voltage. At high bias voltage, the emission intensity depends non-linearly on the optical pump power. The enhanced emission can be modelled by rate equations taking into account hole injection from the tip (anode into the highest occupied orbital of the closest substrate-bound molecule (lower level and radiative recombination with an electron from above the Fermi level (upper level, hence feeding photons back by stimulated emission resonant with the gap mode. The system reflects many essential features of a superluminescent light emitting diode.

  6. The relationship between optical guiding and the relative phase in free-electron lasers

    International Nuclear Information System (INIS)

    Freund, H.P.; Antonsen, T.M. Jr.

    1991-01-01

    In this paper the relationship between the relative phase and optical guiding in the free-electron laser is studied. The relative phase in this case is defined as the shift in the wavenumber from the vacuum value integrated over the interaction length. In terms of the optical guiding of the signal in free-electron lasers, the relative phase must be positive in order for refractive guiding of the signal to occur. The relative phase is studied from the standpoint of the linear stability analysis in both the high- and low-gain regimes, and the qualitative implications in each of these regimes of the relative phase on the refractive guiding of the signal are identical. Specifically, the relative phase is found to be negative at the low-frequency over this band until it turns positive at a frequency approximately 10% below the frequency of peak gain. Thus optical guiding is indicated over a large portion, but not all, of the gain band. A quantitative measure of the optical guiding of the signal is obtained by an analytic formulation of the guiding of the signal. This formulation is based upon a separable beam approximation in which the evolution of the signal is determined by a Green's function analysis. The specific example of interest involves the low-gain regime prior to saturation. In this case, it is shown that the analytic result is in substantial agreement with the calculation of the relative phase

  7. The electronic and optical properties of amorphous silica with hydrogen defects by ab initio calculations

    Science.gov (United States)

    Ren, Dahua; Xiang, Baoyan; Hu, Cheng; Qian, Kai; Cheng, Xinlu

    2018-04-01

    Hydrogen can be trapped in the bulk materials in four forms: interstitial molecular H2, interstitial atom H, O‑H+(2Si=O–H)+, Si‑H‑( {{4O}}\\bar \\equiv {{Si&x2212H}})‑ to affect the electronic and optical properties of amorphous silica. Therefore, the electronic and optical properties of defect-free and hydrogen defects in amorphous silica were performed within the scheme of density functional theory. Initially, the negative charged states hydrogen defects introduced new defect level between the valence band top and conduction band bottom. However, the neutral and positive charged state hydrogen defects made both the valence band and conduction band transfer to the lower energy. Subsequently, the optical properties such as absorption spectra, conductivity and loss functions were analyzed. It is indicated that the negative hydrogen defects caused the absorption peak ranging from 0 to 2.0 eV while the positive states produced absorption peaks at lower energy and two strong absorption peaks arose at 6.9 and 9.0 eV. However, the neutral hydrogen defects just improved the intensity of absorption spectrum. This may give insights into understanding the mechanism of laser-induced damage for optical materials. Project supported by the Science and Technology of Hubei Provincial Department of Education (No. B2017098).

  8. 5 CFR 532.267 - Special wage schedules for aircraft, electronic, and optical instrument overhaul and repair...

    Science.gov (United States)

    2010-01-01

    ... manufacturing. 334418 Printed circuit assembly (electronic assembly) manufacturing. 334419 Other electronic..., electronic, and optical instrument overhaul and repair positions in Puerto Rico. 532.267 Section 532.267 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS PREVAILING RATE SYSTEMS...

  9. A robust fibre laser system for electro-optic electron bunch profile measurements at FLASH

    International Nuclear Information System (INIS)

    Wissmann, Laurens-Georg

    2012-08-01

    For the electro-optic measurement of electron bunch profiles at FLASH a robust ytterbium doped fibre laser (YDFL) system has been developed consisting of a laser oscillator and a two-staged amplifier. The oscillator is designed to meet the specifications of high reliability and low noise operation. The amplifier makes use of tailored nonlinearity to enhance the spectral bandwidth of the output laser pulses. Active repetition rate control enables sub-picosecond synchronisation of the laser to the accelerator reference RF. Using a two-stage gating scheme the output pulse train repetition rate is adopted to the accelerator repetition rate. An experimental site used for electro-optic electron bunch diagnostics has been redesigned to support single-shot bunch profile measurements based on spectral decoding. An existing bunch profile monitor with a similar laser system was upgraded and electro-optic bunch profile measurements were conducted, allowing for a comparison with measurements done with other longitudinal electron bunch diagnostics and with former measurements.

  10. A robust fibre laser system for electro-optic electron bunch profile measurements at FLASH

    Energy Technology Data Exchange (ETDEWEB)

    Wissmann, Laurens-Georg

    2012-08-15

    For the electro-optic measurement of electron bunch profiles at FLASH a robust ytterbium doped fibre laser (YDFL) system has been developed consisting of a laser oscillator and a two-staged amplifier. The oscillator is designed to meet the specifications of high reliability and low noise operation. The amplifier makes use of tailored nonlinearity to enhance the spectral bandwidth of the output laser pulses. Active repetition rate control enables sub-picosecond synchronisation of the laser to the accelerator reference RF. Using a two-stage gating scheme the output pulse train repetition rate is adopted to the accelerator repetition rate. An experimental site used for electro-optic electron bunch diagnostics has been redesigned to support single-shot bunch profile measurements based on spectral decoding. An existing bunch profile monitor with a similar laser system was upgraded and electro-optic bunch profile measurements were conducted, allowing for a comparison with measurements done with other longitudinal electron bunch diagnostics and with former measurements.

  11. Optical and x-ray imaging of electron beams using synchrotron emission

    International Nuclear Information System (INIS)

    Wilke, M.

    1995-01-01

    In the case of very low emittance electron and positron storage ring beams, it is impossible to make intrusive measurements of beam properties without increasing the emittance and possibly disrupting the beam. In cases where electron or positron beams have high average power densities (such as free electron laser linacs), intrusive probes such as wires and optical transition radiation screens or Cherenkov emitting screens can be easily damaged or destroyed. The optical and x-ray emissions from the bends in the storage rings and often from linac bending magnets can be used to image the beam profile to obtain emittance information about the beam. The techniques, advantages and limitations of using both optical and x-ray synchrotron emission to measure beam properties are discussed and the possibility of single bunch imaging is considered. The properties of suitable imagers and converters such as phosphors are described. Examples of previous, existing and planned applications are given where available, including a pinhole imaging system currently being designed for the Advanced Photon Source at Argonne National Laboratory

  12. Optical and x-ray imaging of electron beams using synchrotron emission

    International Nuclear Information System (INIS)

    Wilke, M.D.

    1994-01-01

    In the case of very low eniittance electron and positron storage ring beams, it is impossible to make intrusive measurements of beam properties without increasing the emittance and possibly disrupting the beam. In cases where electron or positron beams have high average power densities (such as free electron laser linacs), intrusive probes such as wires and optical transition radiation screens or Cherenkov emitting screens can be easily damaged or destroyed. The optical and x-ray emissions from the bends in the storage rings and often from linac bending magnets can be used to image the beam profile to obtain emittance information about the beam. The techniques, advantages and limitations of using both optical and x-ray synchrotron emission to measure beam properties are discussed and the possibility of single bunch imaging is considered. The properties of suitable imagers and converters such as phosphors are described. Examples of previous, existing and planned applications are given where available, including a pinhole imaging system currently being designed for the Advanced Photon Source at Argonne National Laboratory

  13. Structural, electronic, and optical properties of GaInO{sub 3}: A hybrid density functional study

    Energy Technology Data Exchange (ETDEWEB)

    Wang, V., E-mail: wangvei@icloud.com; Ma, D.-M.; Liu, R.-J.; Yang, C.-M. [Department of Applied Physics, Xi' an University of Technology, Xi' an 710054 (China); Xiao, W. [State Key Lab of Nonferrous Metals and Processes, General Research Institute for Nonferrous Metals, Beijing 100088 (China)

    2014-01-28

    The structural, electronic, and optical properties of GaInO{sub 3} have been studied by first-principles calculations based on Heyd-Scuseria-Ernzerhof hybrid functional theory. The optical properties, including the optical reflectivity, refractive index, extinction coefficient, absorption coefficient, and electron energy loss are discussed for radiation up to 60 eV together with the calculated electronic structure. Our results predicted that GaInO{sub 3} displays good transparency over the whole vision region, which is in good agreement with the experimental data available in the literature.

  14. Acute optic nerve sheath fenestration with the free-electron laser

    Science.gov (United States)

    Shen, Jin-Hui; Casagrande, Vivien A.; Joos, Karen M.; Shetlar, Debra J.; Robinson, Richard D.; Head, William S.; Mavity-Hudson, Julia A.; Nunnally, Amy H.

    1999-06-01

    Purpose: To determine if the free electron laser (FEL) energy can be delivered to a small space to perform optic nerve sheath fenestration with minimal acute nerve damage. Methods: A 530 mm hollow waveguide probe was designed. Optic nerve sheath fenestration (1.0 mm diameter) was performed in 8 rabbits using either the FEL (4 eyes, 6.45mm, 10 Hz, 2 mJ) or a knife (4 eyes). Within 2 hours following surgery, the animals were perfused with aldehyde fixative. The integrity of the optic nerve and glial response at the site of fenestration were evaluated on tissue selections with H&E, and antibodies to S100β or GFAP. Results: Surgery using the FEL probe was found to be technically superior to the knife. The glial reaction was limited to a zone adjacent to the fenestration and was similar in both the FEL and knife incisions. Conclusions: The FEL appears capable of efficiently performing an optic nerve sheath fenestration in a small space with minimal acute damage. Both the FEL and knife incisions result in a rapid glial response at the site of fenestration even when optic nerve integrity is not compromised.

  15. The conceptualization model problem—surprise

    Science.gov (United States)

    Bredehoeft, John

    2005-03-01

    The foundation of model analysis is the conceptual model. Surprise is defined as new data that renders the prevailing conceptual model invalid; as defined here it represents a paradigm shift. Limited empirical data indicate that surprises occur in 20-30% of model analyses. These data suggest that groundwater analysts have difficulty selecting the appropriate conceptual model. There is no ready remedy to the conceptual model problem other than (1) to collect as much data as is feasible, using all applicable methods—a complementary data collection methodology can lead to new information that changes the prevailing conceptual model, and (2) for the analyst to remain open to the fact that the conceptual model can change dramatically as more information is collected. In the final analysis, the hydrogeologist makes a subjective decision on the appropriate conceptual model. The conceptualization problem does not render models unusable. The problem introduces an uncertainty that often is not widely recognized. Conceptual model uncertainty is exacerbated in making long-term predictions of system performance. C'est le modèle conceptuel qui se trouve à base d'une analyse sur un modèle. On considère comme une surprise lorsque le modèle est invalidé par des données nouvelles; dans les termes définis ici la surprise est équivalente à un change de paradigme. Des données empiriques limitées indiquent que les surprises apparaissent dans 20 à 30% des analyses effectuées sur les modèles. Ces données suggèrent que l'analyse des eaux souterraines présente des difficultés lorsqu'il s'agit de choisir le modèle conceptuel approprié. Il n'existe pas un autre remède au problème du modèle conceptuel que: (1) rassembler autant des données que possible en utilisant toutes les méthodes applicables—la méthode des données complémentaires peut conduire aux nouvelles informations qui vont changer le modèle conceptuel, et (2) l'analyste doit rester ouvert au fait

  16. Calculation of inelastic mean free path and stopping power for electrons in solids from an optical-data model

    International Nuclear Information System (INIS)

    Fernandez-Varea, J.M.; Mayol, R.; Salvat, F.; Liljequist, D.

    1992-11-01

    The numerical calculation of electron inelastic mean free path and stopping power from an optical-data model recently proposed by Fernandez-Varea et al. is described in detail. Explicit expressions for the one-electron total cross sections of the two-modes model of the free-electron gas and the δ-oscillator are derived. The inelastic mean free path and the stopping power are obtained as integrals of these one-electron total cross sections weighted by the optical as integrals of these one-electron total cross sections weighted by the optical oscillator strength. The integrals can be easily evaluated, with a selected accuracy, by using the FORTRAN 77 subroutine GABQ described here, which implements a 20-points Gauss adaptive bipartition quadrature method. Source listings of FORTRAN 77 subroutines to compute the one-electron total cross sections are also given

  17. Optical synchronization of a free-electron laser with femtosecond precision

    Energy Technology Data Exchange (ETDEWEB)

    Loehl, F.

    2009-09-15

    High-gain free-electron lasers (FELs) are capable of generating sub-10 fs long light pulses. In order to take full advantage of these extremely short light pulses in time-resolved experiments, synchronization with a so far unprecedented timing accuracy is required. Within this thesis, an optical synchronization system providing sub-10 fs stability has been developed and was implemented at the ultra-violet and soft X-ray free-electron laser FLASH at DESY, Hamburg. The system uses a mode-locked laser as a timing reference. The laser pulses are distributed via length stabilized optical fiber-links to the remote locations. A key feature of the system is a bunch arrival-time monitor detecting the electron bunch arrival-time with an unrivaled resolution of 6 fs. A feedback system based on the arrival-time monitor was established, improving the arrival-time fluctuations from 200 fs in the unstabilized case to 25 fs with active feedback. In order to achieve the high peak current of several thousand amperes required for the FEL process, the electron bunches are longitudinally compressed in two magnetic chicanes. A second feedback system was developed stabilizing the bunch compression process based on measurements of diffraction radiation. The combination of both feedback systems improves the stability of the FEL radiation significantly. (orig.)

  18. Optical synchronization of a free-electron laser with femtosecond precision

    International Nuclear Information System (INIS)

    Loehl, F.

    2009-09-01

    High-gain free-electron lasers (FELs) are capable of generating sub-10 fs long light pulses. In order to take full advantage of these extremely short light pulses in time-resolved experiments, synchronization with a so far unprecedented timing accuracy is required. Within this thesis, an optical synchronization system providing sub-10 fs stability has been developed and was implemented at the ultra-violet and soft X-ray free-electron laser FLASH at DESY, Hamburg. The system uses a mode-locked laser as a timing reference. The laser pulses are distributed via length stabilized optical fiber-links to the remote locations. A key feature of the system is a bunch arrival-time monitor detecting the electron bunch arrival-time with an unrivaled resolution of 6 fs. A feedback system based on the arrival-time monitor was established, improving the arrival-time fluctuations from 200 fs in the unstabilized case to 25 fs with active feedback. In order to achieve the high peak current of several thousand amperes required for the FEL process, the electron bunches are longitudinally compressed in two magnetic chicanes. A second feedback system was developed stabilizing the bunch compression process based on measurements of diffraction radiation. The combination of both feedback systems improves the stability of the FEL radiation significantly. (orig.)

  19. Ultrafast electron-optical phonon scattering and quasiparticle lifetime in CVD-grown graphene.

    Science.gov (United States)

    Shang, Jingzhi; Yu, Ting; Lin, Jianyi; Gurzadyan, Gagik G

    2011-04-26

    Ultrafast quasiparticle dynamics in graphene grown by chemical vapor deposition (CVD) has been studied by UV pump/white-light probe spectroscopy. Transient differential transmission spectra of monolayer graphene are observed in the visible probe range (400-650 nm). Kinetics of the quasiparticle (i.e., low-energy single-particle excitation with renormalized energy due to electron-electron Coulomb, electron-optical phonon (e-op), and optical phonon-acoustic phonon (op-ap) interactions) was monitored with 50 fs resolution. Extending the probe range to near-infrared, we find the evolution of quasiparticle relaxation channels from monoexponential e-op scattering to double exponential decay due to e-op and op-ap scattering. Moreover, quasiparticle lifetimes of mono- and randomly stacked graphene films are obtained for the probe photon energies continuously from 1.9 to 2.3 eV. Dependence of quasiparticle decay rate on the probe energy is linear for 10-layer stacked graphene films. This is due to the dominant e-op intervalley scattering and the linear density of states in the probed electronic band. A dimensionless coupling constant W is derived, which characterizes the scattering strength of quasiparticles by lattice points in graphene.

  20. Electronic and optical properties of GaN under pressure: DFT calculations

    Science.gov (United States)

    Javaheri, Sahar; Boochani, Arash; Babaeipour, Manuchehr; Naderi, Sirvan

    2017-12-01

    Optical and electronic properties of ZB, RS and WZ structures of gallium nitride (GaN) are studied in equilibrium and under pressure using the first-principles calculation in the density functional theory (DFT) framework to obtain quantities like dielectric function, loss function, reflectance and absorption spectra, refractive index and their relation parameters. The electronic properties are studied using EV-GGA and GGA approximations and the results calculated by EV-GGA approximation were found to be much closer to the experimental results. The interband electron transitions are studied using the band structure and electron transition peaks in the imaginary part of the dielectric function; these transitions occur in three structures from N-2p orbital to Ga-4s and Ga-4p orbitals in the conduction band. Different optical properties of WZ structure were calculated in two polarization directions of (100) and (001) and the results were close to each other. Plasmon energy corresponding to the main peak of the energy-loss function in RS with the value of 26 eV was the highest one, which increased under pressure. In general, RS shows more different properties than WZ and ZB.

  1. Electro-optic sampling for time resolving relativistic ultrafast electron diffraction

    International Nuclear Information System (INIS)

    Scoby, C. M.; Musumeci, P.; Moody, J.; Gutierrez, M.; Tran, T.

    2009-01-01

    The Pegasus laboratory at UCLA features a state-of-the-art electron photoinjector capable of producing ultrashort (<100 fs) high-brightness electron bunches at energies of 3.75 MeV. These beams recently have been used to produce static diffraction patterns from scattering off thin metal foils, and it is foreseen to take advantage of the ultrashort nature of these bunches in future pump-probe time-resolved diffraction studies. In this paper, single shot 2-d electro-optic sampling is presented as a potential technique for time of arrival stamping of electron bunches used for diffraction. Effects of relatively low bunch charge (a few 10's of pC) and modestly relativistic beams are discussed and background compensation techniques to obtain high signal-to-noise ratio are explored. From these preliminary tests, electro-optic sampling is suitable to be a reliable nondestructive time stamping method for relativistic ultrafast electron diffraction at the Pegasus lab.

  2. Optical properties of alkali halide crystals from all-electron hybrid TD-DFT calculations

    Energy Technology Data Exchange (ETDEWEB)

    Webster, R., E-mail: ross.webster07@imperial.ac.uk; Harrison, N. M. [Thomas Young Centre, Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ (United Kingdom); Bernasconi, L. [Rutherford Appleton Laboratory, STFC, Harwell Oxford, Didcot OX11 0QX (United Kingdom)

    2015-06-07

    We present a study of the electronic and optical properties of a series of alkali halide crystals AX, with A = Li, Na, K, Rb and X = F, Cl, Br based on a recent implementation of hybrid-exchange time-dependent density functional theory (TD-DFT) (TD-B3LYP) in the all-electron Gaussian basis set code CRYSTAL. We examine, in particular, the impact of basis set size and quality on the prediction of the optical gap and exciton binding energy. The formation of bound excitons by photoexcitation is observed in all the studied systems and this is shown to be correlated to specific features of the Hartree-Fock exchange component of the TD-DFT response kernel. All computed optical gaps and exciton binding energies are however markedly below estimated experimental and, where available, 2-particle Green’s function (GW-Bethe-Salpeter equation, GW-BSE) values. We attribute this reduced exciton binding to the incorrect asymptotics of the B3LYP exchange correlation ground state functional and of the TD-B3LYP response kernel, which lead to a large underestimation of the Coulomb interaction between the excited electron and hole wavefunctions. Considering LiF as an example, we correlate the asymptotic behaviour of the TD-B3LYP kernel to the fraction of Fock exchange admixed in the ground state functional c{sub HF} and show that there exists one value of c{sub HF} (∼0.32) that reproduces at least semi-quantitatively the optical gap of this material.

  3. Electron spin control and torsional optomechanics of an optically levitated nanodiamond in vacuum

    Science.gov (United States)

    Li, Tongcang; Hoang, Thai; Ahn, Jonghoon; Bang, Jaehoon

    Electron spins of diamond nitrogen-vacancy (NV) centers are important quantum resources for nanoscale sensing and quantum information. Combining such NV spin systems with levitated optomechanical resonators will provide a hybrid quantum system for many novel applications. Here we optically levitate a nanodiamond and demonstrate electron spin control of its built-in NV centers in vacuum. We observe that the strength of electron spin resonance (ESR) is enhanced when the air pressure is reduced. We also observe that oxygen and helium gases have different effects on both the photoluminescence and the ESR contrast of nanodiamond NV centers, indicating potential applications of NV centers in oxygen gas sensing. For spin-optomechanics, it is important to control the orientation of the nanodiamond and NV centers in a magnetic field. Recently, we have observed the angular trapping and torsional vibration of a levitated nanodiamond, which paves the way towards levitated torsional optomechanics in the quantum regime. NSF 1555035-PHY.

  4. Optical Absorption and Electron Injection of 4-(Cyanomethylbenzoic Acid Based Dyes: A DFT Study

    Directory of Open Access Journals (Sweden)

    Yuehua Zhang

    2015-01-01

    Full Text Available Density functional theory (DFT and time-dependent density functional theory (TDDFT calculations were carried out to study the ground state geometries, electronic structures, and absorption spectra of 4-(cyanomethylbenzoic acid based dyes (AG1 and AG2 used for dye-sensitized solar cells (DSSCs. The excited states properties and the thermodynamical parameters of electron injection were studied. The results showed that (a two dyes have uncoplanar structures along the donor unit and conjugated bridge space, (b two sensitizers exhibited intense absorption in the UV-Vis region, and (c the excited state oxidation potential was higher than the conduction band edge of TiO2 photoanode. As a result, a solar cell based on the 4-(cyanomethylbenzoic acid based dyes exhibited well photovoltaic performance. Furthermore, nine dyes were designed on the basis of AG1 and AG2 to improve optical response and electron injection.

  5. The limits of the electron optical parameters of asymmetric double pipecol magnetic objective lenses

    International Nuclear Information System (INIS)

    Al-khashab, A. M.; Abas, K. A.

    1997-01-01

    The asymmetrical magnetic electron lens is of great importance for the electron microscopes intended for high resolution. Such lenses are determined not only by its geometric structure and shape parameters but also by the gap width to bore diameter (S/D) of its pole pieces. a systematic investigation has been carried out for asymmetric objective lenses having different bore diameters. The results indicate that the op per h ore diameter of pole piece lens has considerable effects on the electron optical properties. The Comparison between the two sets of the family of asymmetric lenses provides good performance, and suggests that the ratio of the lens gap width to the bore diameters of its pole pieces (S/ D 1 /D 2 =3) are favourable. (authors). 9 refs., 9 figs

  6. Ionospheric Electron Heating Associated With Pulsating Auroras: Joint Optical and PFISR Observations

    Science.gov (United States)

    Liang, Jun; Donovan, E.; Reimer, A.; Hampton, D.; Zou, S.; Varney, R.

    2018-05-01

    In a recent study, Liang et al. (2017, https://doi.org/10.1002/2017JA024127) repeatedly identified strong electron temperature (Te) enhancements when Swarm satellites traversed pulsating auroral patches. In this study, we use joint optical and Poker Flat Incoherent Scatter Radar (PFISR) observations to further investigate the F region plasma signatures related to pulsating auroras. On 19 March 2015 night, which contained multiple intervals of pulsating auroral activities, we identify a statistical trend, albeit not a one-to-one correspondence, of strong Te enhancements ( 500-1000 K) in the upper F region ionosphere during the passages of pulsating auroras over PFISR. On the other hand, there is no discernible and repeatable density enhancement in the upper F region during pulsating auroral intervals. Collocated optical and NOAA satellite observations suggest that the pulsating auroras are composed of energetic electron precipitation with characteristic energy >10 keV, which is inefficient in electron heating in the upper F region. Based upon PFISR observations and simulations from Liang et al. (2017) model, we propose that thermal conduction from the topside ionosphere, which is heated by precipitating low-energy electrons, offers the most likely explanation for the observed electron heating in the upper F region associated with pulsating auroras. Such a heating mechanism is similar to that underlying the "stable auroral red arcs" in the subauroral ionosphere. Our proposal conforms to the notion on the coexistence of an enhanced cold plasma population and the energetic electron precipitation, in magnetospheric flux tubes threading the pulsating auroral patch. In addition, we find a trend of enhanced ion upflows during pulsating auroral intervals.

  7. Optical and Morphological Properties of Electron-Beam Irradiated High-Density Thin Poly Ethylene Films

    International Nuclear Information System (INIS)

    Abdel-Hamid, H. M.; Fawzy, Y.H.A.; El-Sayed, S.M.

    2005-01-01

    Effects of surface morphology alterations on the optical properties of the high-density polyethylene (HDPE) films irradiated by 1.5 MeV electron beam has been investigated. The irradiation doses were conducted at the values: 30, 135, 295 and 540 kGy, respectively. The changes induced in HDPE involved: the creation of free radicals, the formation of chemical bonds i.e., intermolecular crosslinking and irreversible cleavage of bonds in the main chain, which resulted in the fragmentation of the molecules. An Ultraviolet-Visible Spectrophotometer (UV-VIS) and Scanning Electron Microscope (SEM) were used to characterize the changes. Because the crosslinking (induced by electron irradiation) limits the movability of the HDPE molecular chains, the optical energy gap was then subjected to a change. It decreased from 4.41 to 3.22 eV with an increasing electron dose up to 540 kGy. At a higher dose of irradiation (540 kGy), degradation of HDPE rather than crosslinking was raised. The irradiated HDPE films indicated that the crosslinking and degradation are likely to have an effect on their surface morphologies. The physical properties of polymeric materials can be modified by ionizing radiation in the form of gamma rays, X-rays and energetic electrons. High-energy electron beam is an especially useful tool in this regard (Cleland et al, 2003). Polymerizing, grafting, crosslinking and chain scission reactions can be initiated by irradiation. The results of such reactions can enhance the utility and value of commercial products. HDPE (CH2-CH2) has many attractive properties, such as an excellent chemical resistance, low friction and low moisture absorption

  8. DMSP optical and electron measurements in the vicinity of polar cap arcs

    International Nuclear Information System (INIS)

    Hardy, D.A.; Burke, W.J.; Gussenhoven, M.S.

    1982-01-01

    We have completed an extensive analysis of the electron and optical data from the DMSP satellites for an external period of polar cap arc occurrences on December 12, 1977. The polar cap arcs are observed in three distinct intervals in a period of quieting after a time of intense substorm activity. The observation of polar cap arcs is associated with the admittance of large and variable fluxes of low-energy electrons into a major portion of both the northern and southern hemisphere polar caps. These fluxes fall into the following categories: First, nearly Maxwellian distributions of electrons with temperatures between 50 eV and 200 eV and number densities varying from 0.03/cm 3 to 4/cm 3 . The highest densities are found at the poleward boundary of the diffuse aurorae and near the visible polar cap arcs. The lowest densities are associated with the polar rain. Second, distributions of electrons peaked between 50 eV and 200 eV. These distributions result from accelertion of the cold Maxwellian distribution through a potential of 50 to 200 V without any heating of the electrons. Third, distributions of electrons displaying two populations; an intense low-energy component with a temperature of approx.20 eV and a much weaker high-energy component with a temperature of 180 eV. We interpret such distributions as evidence of direct admittance of magnetosheath electrons into the polar cap. Fourth,, distributions of electrons peaked at approx.1 keV. These distributions produce the visible arcs. They result from the acceleration of a two-component electron population with temperatures of 100 and 350 eV through a potential drop of approx.750 V

  9. Progress in Studies of Electron-Cloud-Induced Optics Distortions at CesrTA

    International Nuclear Information System (INIS)

    Crittenden, James; Penn, Gregory; Venturini, Marco; Harkay, Katherine; Holtzapple, Robert; Pivi, Mauro; Wang, Lanfa

    2012-01-01

    The Cornell Electron Storage Ring Test Accelerator (CesrTA) program has included extensive measurements of coherent betatron tune shifts for a variety of electron and positron beam energies, bunch population levels, and bunch train configurations. The tune shifts have been shown to result primarily from the interaction of the beam with the space-charge field of the beam-induced low-energy electron cloud in the vacuum chamber. Comparison to several advanced electron cloud simulation codes has allowed determination of the sensitivity of these measurements to physical parameters characterizing the synchrotron radiation flux, the production of photo-electrons on the vacuum chamber wall, the beam emittance, lattice optics, and the secondary-electron yield model. We report on progress in understanding the cloud buildup and decay mechanisms in magnetic fields and in field-free regions, addressing quantitatively the precise determination of the physical parameters of the modeling. Validation of these models will serve as essential input in the design of damping rings for future high-energy linear colliders.

  10. An integrated electron and optical metallographic procedure for the identification of precipitate phases in type 316 stainless steel

    International Nuclear Information System (INIS)

    Slattery, G.F.; O'Riordan, P.; Lambert, M.E.; Green, S.M.

    1981-01-01

    A sequential and integrated metallographic procedure has been developed and successfully employed to differentiate between carbide, sigma, chi, Laves and ferrite phases which are commonly encountered in type 316 austenitic steel. The experimental techniques of optical and electron microscopy to identify these phases have been outlined and provide a rapid and convenient method of characterizing the microstructure of the steel. The techniques sequence involves selective metallographic etching, Nomarski interference microscopy, scanning electron microscopy, energy dispersive microanalysis, transmission electron microscopy and electron diffraction. (author)

  11. Electronic band structure and optical properties of Srn+1TinO3n+1 Ruddlesden-Popper homologous series

    Czech Academy of Sciences Publication Activity Database

    Reshak, Ali H; Auluck, S.; Kityk, I.

    2008-01-01

    Roč. 47, č. 7 (2008), s. 5516-5520 ISSN 0021-4922 Institutional research plan: CEZ:AV0Z60870520 Keywords : electronic structure * optical properties Subject RIV: BO - Biophysics Impact factor: 1.309, year: 2008

  12. X-rays from comets - a surprising discovery

    CERN Document Server

    CERN. Geneva

    2000-01-01

    Comets are kilometre-size aggregates of ice and dust, which remained from the formation of the solar system. It was not obvious to expect X-ray emission from such objects. Nevertheless, when comet Hyakutake (C/1996 B2) was observed with the ROSAT X-ray satellite during its close approach to Earth in March 1996, bright X-ray emission from this comet was discovered. This finding triggered a search in archival ROSAT data for comets, which might have accidentally crossed the field of view during observations of unrelated targets. To increase the surprise even more, X-ray emission was detected from four additional comets, which were optically 300 to 30 000 times fainter than Hyakutake. For one of them, comet Arai (C/1991 A2), X-ray emission was even found in data which were taken six weeks before the comet was optically discovered. These findings showed that comets represent a new class of celestial X-ray sources. The subsequent detection of X-ray emission from several other comets in dedicated observations confir...

  13. Optical Response of Warm Dense Matter Using Real-Time Electron Dynamics

    Science.gov (United States)

    Baczewski, Andrew; Shulenburger, Luke; Desjarlais, Michael; Magyar, Rudolph

    2014-03-01

    The extreme temperatures and solid-like densities in warm dense matter present a unique challenge for theory, wherein neither conventional models from condensed matter nor plasma physics capture all of the relevant phenomenology. While Kubo-Greenwood DFT calculations have proven capable of reproducing optical properties of WDM, they require a significant number of virtual orbitals to reach convergence due to their perturbative nature. Real-time TDDFT presents a complementary framework with a number of computationally favorable properties, including reduced cost complexity and better scalability, and has been used to reproduce the optical response of finite and ordered extended systems. We will describe the use of Ehrenfest-TDDFT to evolve coupled electron-nuclear dynamics in WDM systems, and the subsequent evaluation of optical response functions from the real-time electron dynamics. The advantages and disadvantages of this approach will be discussed relative to the current state-of-the-art. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Security Administration under contract DE-AC04-94AL85000.

  14. Optical and electronic properties of microcrystalline silicon as a function of microcrystallinity

    International Nuclear Information System (INIS)

    Han, Daxing; Yue, Guozhen; Lorentzen, J. D.; Lin, Jing; Habuchi, H.; Wang, Qi

    2000-01-01

    Films were prepared by hot wire chemical vapor deposition at ∼240 degree sign C with varied hydrogen dilution ratios R=H 2 :SiH 4 from 1 to 20. The optical and electronic properties as a function of microcrystallinity were studied. We found: (a) At low H dilution R≤2, there is no measurable crystallinity by Raman spectroscopy and x-ray diffraction in the a-Si:H matrix, but an optical absorption peak at ∼1.25 eV appears; when R=2, the film shows the lowest subgap absorption, the highest photosensitivity, and the largest optical gap. (b) When R≥3, the c-Si phase is measurable by Raman and a low-energy photoluminescence (PL) band (0.84-1.0 eV) appears in addition to the high-energy band (1.3-1.4 eV). Meanwhile, all the absorption spectra show a featureless line shape. (c) An energy redshift is observed for both PL peaks as the film grows thicker. Finally, (d) the conductivity activation energy first decreases from 0.68 to 0.12 eV, then increases with increasing microcrystallinity. A mode of two sets of energy bands of electronic states for these two-phase materials is suggested. (c) 2000 American Institute of Physics

  15. 'Diffraction-free' optical beams in inverse free electron laser accelerators

    International Nuclear Information System (INIS)

    Cai, S.Y.; Bhattacharjee, A.; Marshall, T.C.

    1988-01-01

    'Diffraction-free' optical beams correspond to exact solutions of the wave equation in free space with the remarkable property that they propagate with negligible transverse spreading for distances much larger than the Rayleigh range. The requirement for this to occur is a large aperture. Using a 2D computer code, we find that these optical beams will also propagate with negligible diffraction even when perturbed by the electron beam in an IFEL; indeed they match well the FEL requirement for the accelerator. The numerical simulations are performed for the proposed facility at Brookhaven in which λ s =10 μm, B=1.5 T (linearly tapered l w =1.31-6.28 cm) and the optical beam power is either 8x10 11 W or 2.3x10 10 W. Approximately 70% of the electrons constituting a beam of current 5 mA or 15 A, radius 0.14 mm and initial energy of 50 MeV is accelerated at 50 MeV/m. (orig.)

  16. Formation of low time-bandwidth product, single-sided exponential optical pulses in free-electron laser oscillators

    NARCIS (Netherlands)

    MacLeod, A. M.; Yan, X.; Gillespie, W. A.; Knippels, G.M.H.; Oepts, D.; van der Meer, A. F. G.; Rella, C. W.; Smith, T. J.; Schwettman, H. A.

    2000-01-01

    The detailed shape of picosecond optical pulses from a free-electron laser (FEL) oscillator has been studied for various cavity detunings. For large values of the cavity detuning the optical pulse develops an exponential leading edge, with a time constant proportional to the applied cavity detuning

  17. Wavelength-selective bleaching of the optical spectra of trapped electrons in organic glasses. II

    International Nuclear Information System (INIS)

    Paraszczak, J.; Willard, J.E.

    1979-01-01

    Further resolution of the inhomogeneous optical spectra of trapped electrons (e - /sub t/) in organic glasses has been obtained from wavelength selective bleaching and thermal decay studies on 3-methylpentane-d 14 (3MP-d 14 ) and 2-methyltetrahydrofuran (MTHF) following γ irradiation in the temperature region of 20 K, and limits on the degree of resolution achievable have been indicated. Exposure of 3MP-d 14 to light of wavelengths >2100 nm (from a tunable laser) reduces the optical densities at the bleaching wavelength and longer to zero, while ''peeling off'' a portion of the O.D. at all shorter wavelengths but leaving the remainder of the spectrum unaffected. The fraction of the integrated optical spectrum, ∫OD d (eV), removed by bleaching at each wavelength tested, and also by thermal decay, is equivalent to the fraction of the total e - /sub t/ spins removed and measured by ESR. 1064 nm light bleaches the spectrum nearly uniformly, confirming that the spectra of all of the e - /sub t/ have blue tails with similar ease of bleaching. Heretofore unobserved low temperature thermal decay of e - /sub t/ occurs at 20 and 40 K (20% of the spin concentration in 30 min, 35% in 3h). The rate of decay of the optical spectrum decreases with decreasing wavelength of observation (2.5, 2.2, 1.8, and 1.5 μ), but at each wavelength is the same at 40 K as at 20 K, consistent

  18. Electronic band structures and optical properties of type-II superlattice photodetectors with interfacial effect.

    Science.gov (United States)

    Qiao, Peng-Fei; Mou, Shin; Chuang, Shun Lien

    2012-01-30

    The electronic band structures and optical properties of type-II superlattice (T2SL) photodetectors in the mid-infrared (IR) range are investigated. We formulate a rigorous band structure model using the 8-band k · p method to include the conduction and valence band mixing. After solving the 8 × 8 Hamiltonian and deriving explicitly the new momentum matrix elements in terms of envelope functions, optical transition rates are obtained through the Fermi's golden rule under various doping and injection conditions. Optical measurements on T2SL photodetectors are compared with our model and show good agreement. Our modeling results of quantum structures connect directly to the device-level design and simulation. The predicted doping effect is readily applicable to the optimization of photodetectors. We further include interfacial (IF) layers to study the significance of their effect. Optical properties of T2SLs are expected to have a large tunable range by controlling the thickness and material composition of the IF layers. Our model provides an efficient tool for the designs of novel photodetectors.

  19. Optical properties and electronic structure of the Cu–Zn brasses

    International Nuclear Information System (INIS)

    Keast, V.J.; Ewald, J.; De Silva, K.S.B.; Cortie, M.B.; Monnier, B.; Cuskelly, D.; Kisi, E.H.

    2015-01-01

    The color of Cu–Zn brasses range from the red of copper through bright yellow to grey-silver as the Zn content increases. Here we examine the mechanism by which these color changes occur. The optical properties of this set of alloys has been calculated using density functional theory (DFT) and compared to experimental spectroscopy measurements. The optical response of the low Zn content α-brasses is shown to have a distinctly different origin to that in the higher content β′, γ and ε-brasses. The response of β′-brass is unique in that it is strongly influenced by an overdamped plasmon excitation and this alloy will also have a strong surface plasmon response. - Highlights: • Study of the electronic structure and optical response of the Cu–Zn brasses. • Agreement between experiment and calculation of the dielectric functions. • α-brasses optical response is dominated by transitions from the top of the d-band. • In the other brasses it is transitions around the Fermi level. • β′-brass response is dominateed by an overdamped bulk plasmonic response

  20. Optical and Optoelectronic Property Analysis of Nanomaterials inside Transmission Electron Microscope.

    Science.gov (United States)

    Fernando, Joseph F S; Zhang, Chao; Firestein, Konstantin L; Golberg, Dmitri

    2017-12-01

    In situ transmission electron microscopy (TEM) allows one to investigate nanostructures at high spatial resolution in response to external stimuli, such as heat, electrical current, mechanical force and light. This review exclusively focuses on the optical, optoelectronic and photocatalytic studies inside TEM. With the development of TEMs and specialized TEM holders that include in situ illumination and light collection optics, it is possible to perform optical spectroscopies and diverse optoelectronic experiments inside TEM with simultaneous high resolution imaging of nanostructures. Optical TEM holders combining the capability of a scanning tunneling microscopy probe have enabled nanomaterial bending/stretching and electrical measurements in tandem with illumination. Hence, deep insights into the optoelectronic property versus true structure and its dynamics could be established at the nanometer-range precision thus evaluating the suitability of a nanostructure for advanced light driven technologies. This report highlights systems for in situ illumination of TEM samples and recent research work based on the relevant methods, including nanomaterial cathodoluminescence, photoluminescence, photocatalysis, photodeposition, photoconductivity and piezophototronics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Optical properties and electronic structure of the Cu–Zn brasses

    Energy Technology Data Exchange (ETDEWEB)

    Keast, V.J., E-mail: vicki.keast@newcastle.edu.au [School of Mathematical and Physical Sciences, The University of Newcastle, Callaghan, NSW 2308 (Australia); Ewald, J. [School of Mathematical and Physical Sciences, The University of Newcastle, Callaghan, NSW 2308 (Australia); De Silva, K.S.B.; Cortie, M.B. [Institute for Nanoscale Technology, University of Technology Sydney, PO Box 123, Broadway, NSW 2007 (Australia); Monnier, B. [School of Engineering, The University of Newcastle, Callaghan, NSW 2308 (Australia); Universite de Technologie de Troyes, 12 Rue Marie Curie, BP 2060, 10010 Troyes Cedex (France); Cuskelly, D.; Kisi, E.H. [School of Engineering, The University of Newcastle, Callaghan, NSW 2308 (Australia)

    2015-10-25

    The color of Cu–Zn brasses range from the red of copper through bright yellow to grey-silver as the Zn content increases. Here we examine the mechanism by which these color changes occur. The optical properties of this set of alloys has been calculated using density functional theory (DFT) and compared to experimental spectroscopy measurements. The optical response of the low Zn content α-brasses is shown to have a distinctly different origin to that in the higher content β′, γ and ε-brasses. The response of β′-brass is unique in that it is strongly influenced by an overdamped plasmon excitation and this alloy will also have a strong surface plasmon response. - Highlights: • Study of the electronic structure and optical response of the Cu–Zn brasses. • Agreement between experiment and calculation of the dielectric functions. • α-brasses optical response is dominated by transitions from the top of the d-band. • In the other brasses it is transitions around the Fermi level. • β′-brass response is dominateed by an overdamped bulk plasmonic response.

  2. Optical and mechanical design for 1 nm resolution Auger spectroscopy in an electron microscope

    International Nuclear Information System (INIS)

    Bleeker, A.J.

    1991-01-01

    Detailed information about the atomic structure of surfaces and interfaces is vital for the progress in materials science and physics. One widely used surface sensitive technique is Auger spectroscopy (AS). This technique, in which the electron energy spectrum emerging from the sample is evaluated, gives information about the average elemental composition of the surface over a relative large surface area (>30nm). Electron microscopy (EM), on the other hand, is capable of producing surface structural, but no elemental, information with almost atomic resolution. EM and AS techniques have not been combined so far because of the different nature of the instrumentation used in both techniques. In AS instruments the sample is placed in an Ultra High Vacuum (UHV) system with a relatively large open space around the sample. In EM the sample is situated in the tight volume between the magnetic polepieces of the probe forming objective lens. The space around the sample is therefore tight. Furthermore the vacuum in most electron microscopes is not in UHV range. Radical mechanical changes to improve the vacuum are necessary to do AS in an electron microscope. Since the sample is immersed in the strong magnetic field of the objective lens the Auger electrons can not be extracted with conventional electrostatical methods. The only possibility to extract the Auger electrons is through the upper bore of the objective lens. However, this has large implications on the optical system of the microscope and requires a thorough investigation of the extraction of the Auger electrons. In this work it will be discussed how the surface sensitive AS can be combined with the high spatial resolution of the electron microscope in a practical instrument. (author). 102 refs.; 81 figs.; 4 tabs

  3. Reflective optical system for time-resolved electron bunch measurements at PITZ

    Energy Technology Data Exchange (ETDEWEB)

    Rosbach, K; Baehr, J [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Roensch-Schulenburg, J [Hamburg Univ. (Germany). Inst. fuer Experimentalphysik

    2011-01-15

    The Photo-Injector Test facility at DESY, Zeuthen site (PITZ), produces pulsed electron beams with low transverse emittance and is equipped with diagnostic devices for measuring various electron bunch properties, including the longitudinal and transverse electron phase space distributions. The longitudinal bunch structure is recorded using a streak camera located outside the accelerator tunnel, connected to the diagnostics in the beam-line stations by an optical system of about 30 m length. This system mainly consists of telescopes of achromatic lenses, which transport the light pulses and image them onto the entrance slit of the streak camera. Due to dispersion in the lenses, the temporal resolution degrades during transport. This article presents general considerations for time-resolving optical systems as well as simulations and measurements of specific candidate systems. It then describes the development of an imaging system based on mirror telescopes which will improve the temporal resolution, with an emphasis on off-axis parabolic mirror systems working at unit magnification. A hybrid system of lenses and mirrors will serve as a proof of principle. (orig.)

  4. Inhomogeneous electron distribution in InN nanowires: Influence on the optical properties

    Energy Technology Data Exchange (ETDEWEB)

    Molina-Sanchez, A.; Garro, N.; Garcia-Cristobal, A.; Cantarero, A. [Instituto de Ciencia de los Materiales, Universidad de Valencia (Spain); Segura-Ruiz, J. [European Synchrotron Radiation Facility, Experiments Div., Grenoble (France); Iikawa, F. [Instituto de Fisica Gleb Wataghin - Unicamp, CP 6165, Campinas (Brazil); Denker, C.; Malindretos, J.; Rizzi, A. [IV. Physikalisches Institut, Georg-August Universitaet Goettingen (Germany)

    2012-03-15

    In this work, we study theoretically and experimentally the influence of the surface electron accumulation on the optical properties of InN nanowires. For this purpose, the photoluminescence and photoluminescence excitation spectra have been measured for a set of self-assembled InN NWs grown under different conditions. The photoluminescence excitation experimental lineshapes have been reproduced by a self-consistent calculation of the absorption in a cylindrical InN nanowires. With the self-consistent model we can explore how the optical absorption depends on nanowires radius and doping concentration. Our model solves the Schroedinger equation for a cylindrical nanowire of infinite length, assuming a parabolic conduction band. The columnar geometry introduces effects in both the electron density and in the self-consistent conduction band profile, with no equivalence in planar layer. On the other hand, the differences in the photoluminescence excitation spectra are related to the inhomogeneous electron distribution inside the nanowires, caused by a bulk donor concentration and a two-dimensional density of ionized surface states. For nanowire radii larger than 30 nm, such concentrations modify the absorption edge and the lineshape, respectively, and can be determined from the comparison with the experimental data (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. ELECTRON BUNCH CHARACTERIZATION WITH SUBPICOSECOND RESOLUTION USING ELECTRO-OPTIC TECHNIQUE

    International Nuclear Information System (INIS)

    SEMERTZIDIS, Y.K.; CASTILLO, V.; LARSEN, R.; LAZARUS, D.M.; NIKAS, D.; OZBEN, C.; SRINIVASAN-RAO, T.; STILLMAN, A.; TSANG, T.; KOWALSKI, L.

    2001-01-01

    In the past decade, the bunch lengths of electrons in accelerators have decreased dramatically and are in the range off a few millimeters. Measurement of the length as well as the longitudinal profile of these short bunches have been a topic of research in a number of institutions. One of the techniques uses the electric field induced by the passage of electrons in the vicinity of a birefringent crystal to change its optical characteristics. Well-established electro-optic techniques can then be used to measure the temporal characteristics of the electron bunch. The inherent fast response of the crystal facilitates the measurement to femtosecond time resolution. However, the resolution in experiments so far has been limited to 70 ps, by the bandwidth of the detection equipment. Use of a streak camera can improve this resolution to a few picoseconds. In this paper we present a novel, non-invasive, single-shot approach to improve the resolution to tens of femtoseconds so that sub mm bunch length can be measured

  6. NaAuS chicken-wire-like semiconductor: Electronic structure and optical properties

    International Nuclear Information System (INIS)

    Reshak, A.H.; Khan, Saleem Ayaz; Kamarudin, H.; Bila, Jiri

    2014-01-01

    Highlights: • Chicken wire like semiconductor NaAuS was investigated. • Good agreement with experimental data was found. • Electronic charge density of chicken wire like semiconductor NaAuS was obtained. • The calculated uniaxial anisotropy is −0.0005, indicating the strong anisotropy. -- Abstract: The electronic structure, charge density and optical properties of NaAuS a chicken-wire-like semiconductor was calculated using full potential linear augmented plane wave based on density functional theory. The Ceperley-Alder local density approximation, Perdew Becke Ernzerhof Generalized gradient approximation and Engel Voskov Generalized Gradient Approximation were applied to solve the exchange correlation potential. The investigation of band structures and density of states elucidates that Engle Vasko Generalized Gradient Approximation shows close agreement to the experimental data. The calculated valence charge density shows pure ionic nature of Au–Au bond. It becomes partially covalent when Au is connected with two Na atoms. The linear optical susceptibilities of chicken-wire-like NaAuS semiconductor are calculated so as to obtain further insight into the electronic properties. The uniaxial anisotropy is −0.0005, indicating the strong anisotropy of the dielectric function in the NaAuS a chicken-wire-like semiconductor

  7. NaAuS chicken-wire-like semiconductor: Electronic structure and optical properties

    Energy Technology Data Exchange (ETDEWEB)

    Reshak, A.H. [Institute of Complex Systems, FFPW, CENAKVA, University of South Bohemia in CB, Nove Hrady 37333 (Czech Republic); Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia); Khan, Saleem Ayaz, E-mail: sayaz_usb@yahoo.com [Institute of Complex Systems, FFPW, CENAKVA, University of South Bohemia in CB, Nove Hrady 37333 (Czech Republic); Kamarudin, H. [Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia); Bila, Jiri [Department of Instrumentation and Control Engineering, Faculty of Mechanical Engineering, CTU in Prague, Technicka 4, 166 07 Prague 6 (Czech Republic)

    2014-01-05

    Highlights: • Chicken wire like semiconductor NaAuS was investigated. • Good agreement with experimental data was found. • Electronic charge density of chicken wire like semiconductor NaAuS was obtained. • The calculated uniaxial anisotropy is −0.0005, indicating the strong anisotropy. -- Abstract: The electronic structure, charge density and optical properties of NaAuS a chicken-wire-like semiconductor was calculated using full potential linear augmented plane wave based on density functional theory. The Ceperley-Alder local density approximation, Perdew Becke Ernzerhof Generalized gradient approximation and Engel Voskov Generalized Gradient Approximation were applied to solve the exchange correlation potential. The investigation of band structures and density of states elucidates that Engle Vasko Generalized Gradient Approximation shows close agreement to the experimental data. The calculated valence charge density shows pure ionic nature of Au–Au bond. It becomes partially covalent when Au is connected with two Na atoms. The linear optical susceptibilities of chicken-wire-like NaAuS semiconductor are calculated so as to obtain further insight into the electronic properties. The uniaxial anisotropy is −0.0005, indicating the strong anisotropy of the dielectric function in the NaAuS a chicken-wire-like semiconductor.

  8. The role of ligands in the optical and electronic spectra of CdSe nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Kilina, Svletana [Los Alamos National Laboratory; Sergei, Ivanov A [Los Alamos National Laboratory; Victor, Klimov I [Los Alamos National Laboratory; Sergei, Tretiak [Los Alamos National Laboratory

    2008-01-01

    We investigate the impact of ligands on morphology, electronic structure, and optical response of the Cd33Se33 cluster, which already overlapps in size with the smallest synthesized CdSe quantum dots (QDs). Our Density Functional Theory (DFT) calculations demonstrate significant surface reorganization both for the bare cluster and for the cluster capped by amine and phosphine oxide ligand models. We observe strong surface-ligand interactions leading to substantial charge redistribution and polarization effects on the surface. This effect results in the appearance of hybridized states, where the electronic density is spread over the cluster and the ligands. Neither the ligand's nor hybridized molecular orbitals appear as trap states inside or near the band gap of the QD. Instead, being optically dark, dense hybridized states from the edges of the valence and the conduction bands could open new relaxation channels for high energy photoexcitations. Comparing quantum dots passivated by different ligands, we found that hybridized states are denser in at the edge of the conduction band of the cluster ligated with phosphine oxide molecules than that with primary amines. Such a different manifestation of ligand binding may potentially lead to the faster electron relaxation in dots passivated by phosphine oxide than by amine ligands, which is in agreement with experimental data.

  9. First principles study of structural, electronic and optical properties of polymorphic forms of Rb 2Te

    Science.gov (United States)

    Alay-e-Abbas, S. M.; Shaukat, A.

    2011-05-01

    First-principles density functional theory calculations have been performed for structural, electronic and optical properties of three polymorphic forms of rubidium telluride. Our calculations show that the sequence of pressure induced phase transitions for Rb 2Te is Fm3¯m → Pnma → P6 3/mmc which is governed by the coordination numbers of the anions. From our calculated low transition pressure value for the Fm3¯m phase to the Pnma phase transition of Rb 2Te, the experimentally observed meta-stability of Fm3¯m phase at ambient conditions seems reasonable. The electronic band structure has been calculated for all the three phases and the change in the energy band gap is discussed for the transitioning phases. The energy band gaps obtained for the three phases of Rb 2Te decrease on going from the meta-stable phase to the high-pressure phases. Total and partial density of states for the polymorphs of Rb 2Te has been computed to elucidate the contribution of various atomic states on the electronic band structure. Furthermore, optical properties for all the polymorphic forms have been presented in form of the complex dielectric function.

  10. Electronically conductive perovskite-based oxide nanoparticles and films for optical sensing applications

    Science.gov (United States)

    Ohodnicki, Jr., Paul R; Schultz, Andrew M

    2015-04-28

    The disclosure relates to a method of detecting a change in a chemical composition by contacting a electronically conducting perovskite-based metal oxide material with a monitored stream, illuminating the electronically conducting perovskite-based metal oxide with incident light, collecting exiting light, monitoring an optical signal based on a comparison of the incident light and the exiting light, and detecting a shift in the optical signal. The electronically conducting perovskite-based metal oxide has a perovskite-based crystal structure and an electronic conductivity of at least 10.sup.-1 S/cm, where parameters are specified at the gas stream temperature. The electronically conducting perovskite-based metal oxide has an empirical formula A.sub.xB.sub.yO.sub.3-.delta., where A is at least a first element at the A-site, B is at least a second element at the B-site, and where 0.8perovskite-based oxides include but are not limited to La.sub.1-xSr.sub.xCoO.sub.3, La.sub.1-xSr.sub.xMnO.sub.3, LaCrO.sub.3, LaNiO.sub.3, La.sub.1-xSr.sub.xMn.sub.1-yCr.sub.yO.sub.3, SrFeO.sub.3, SrVO.sub.3, La-doped SrTiO.sub.3, Nb-doped SrTiO.sub.3, and SrTiO.sub.3-.delta..

  11. Electronic-Optical Amplifier in the measurement of light polarization plane

    International Nuclear Information System (INIS)

    Miranda Diaz, Lazaro

    2009-01-01

    This paper analyzes the behavior of the output response of two electronic-optical amplifiers with constant amplitude and phase variable, in which photodiodes each them are arranged spatially 90th each other and both with their faces detection parallel to the axis of light transmission. Outward both amplifiers are going to a digital circuit that compares the fronts outputs to the front of the pulse signal that feeds the light source, to finally obtain the difference in time when fronts of light capture the photodiodes. This configuration permit to analyze the influence of the geometric arrangement of the system optical and understand the principle of why the diodes with their faces parallel to the axis of light transmission are capable of capturing variations of this, and even detect the rotation of the plane of light polarized. (Author)

  12. Influence of Sc doping concentration on electronic structure and optical properties of ZnO

    International Nuclear Information System (INIS)

    Wu Yuxi; Zhang Hao; Han Long; Qu Licheng; Gu Shulin; Li Teng

    2011-01-01

    In this paper, we adopt the density functional theory (DFT) plane wave pseudopotential method to study the crystal structure, electronic structure and optical property for the different concentrations of Sc doped ZnO system. We optimize the structure of Sc and get the basis of numerical simulation. The results show that with the adoption of Sc, the lattice constants of the system increase gradually, the energy of the system becomes larger, the Fermi level enters into the conduction band, the system shows Metallic gradually and the band gap becomes wider. On the other hand, certain changes of the optical properties of doped ZnO have taken place, i. e., a new absorption peak happens in ZnO absorption spectrum and the blue shift of absorption edge with the new peak occurs in the imagery part of dielectric function. (authors)

  13. Electronic structure and optical properties of Al and Mg co-doped GaN

    International Nuclear Information System (INIS)

    Ji Yan-Jun; Du Yu-Jie; Wang Mei-Shan

    2013-01-01

    The electronic structure and optical properties of Al and Mg co-doped GaN are calculated from first principles using density function theory with the plane-wave ultrasoft pseudopotential method. The results show that the optimal form of p-type GaN is obtained with an appropriate Al:Mg co-doping ratio rather than with only Mg doping. Al doping weakens the interaction between Ga and N, resulting in the Ga 4s states moving to a high energy region and the system band gap widening. The optical properties of the co-doped system are calculated and compared with those of undoped GaN. The dielectric function of the co-doped system is anisotropic in the low energy region. The static refractive index and reflectivity increase, and absorption coefficient decreases. This provides the theoretical foundation for the design and application of Al—Mg co-doped GaN photoelectric materials

  14. Adaptive Optics System with Deformable Composite Mirror and High Speed, Ultra-Compact Electronics

    Science.gov (United States)

    Chen, Peter C.; Knowles, G. J.; Shea, B. G.

    2006-06-01

    We report development of a novel adaptive optics system for optical astronomy. Key components are very thin Deformable Mirrors (DM) made of fiber reinforced polymer resins, subminiature PMN-PT actuators, and low power, high bandwidth electronics drive system with compact packaging and minimal wiring. By using specific formulations of fibers, resins, and laminate construction, we are able to fabricate mirror face sheets that are thin (2 KHz. By utilizing QorTek’s proprietary synthetic impendence power supply technology, all the power, control, and signal extraction for many hundreds to 1000s of actuators and sensors can be implemented on a single matrix controller printed circuit board co-mounted with the DM. The matrix controller, in turn requires only a single serial bus interface, thereby obviating the need for massive wiring harnesses. The technology can be scaled up to multi-meter aperture DMs with >100K actuators.

  15. Electronic, optical, and thermoelectric properties of Fe2+xV1−xAl

    Directory of Open Access Journals (Sweden)

    D. P. Rai

    2017-04-01

    Full Text Available We report the electronic, optical, and thermoelectric properties of full-Heusler alloy Fe2VAl with Fe antisite doping (Fe2+xV1−xAl as obtained from the first-principles Tran-Blaha modified Becke-Johnson potential. The results are discussed in relation to the available experimental data and show good agreements for the band gap, magnetic moment, and optical spectra. Exploring our transport data for thermoelectric applicability suggest that Fe2+xV1−xAl is a good candidate with a high figure of merit (ZT 0.75(0.65 for x = 0.25(0.50 at room temperature.

  16. Electronic structure and optical properties in ZnO:M(Co, Cd)

    International Nuclear Information System (INIS)

    Palacios, P.; Aguilera, I.; Wahnon, P.

    2010-01-01

    ZnO doped with some transitions metals (ZnO:M) has several significant potential application. ZnO:Co is proposed to be used in advanced spintronic devices due to its high Curie temperature and large magnetic moments per transition metal. ZnO:Cd has potential applications in short-wavelength optoelectronic devices. This work focuses on an ab-initio study of the electronic and optical properties of ZnO:M doped with Co, and Cd. Theoretical calculations have been done with different computational codes, using the density functional theory (DFT) at the GGA and GGA+U level. The latter introduces a Hubbard term correction in the 'd' levels of the Zn and Co. We used different supercells in order to have different realistic dilution levels which can be achieved in experiments. Doping effects on the features of the optical absorption are also studied and analysed in this work.

  17. Optical band gap of ZnO thin films deposited by electron beam evaporation

    International Nuclear Information System (INIS)

    Nadeem, M. Y.; Ali, S. L.; Wasiq, M. F.; Rana, A. M.

    2006-01-01

    Optical band gap of ZnO thin films deposited by electron beam evaporation at evaporation rates ranging 5 As/sup -1/ to 15 As /sup -1/ and thickness ranging 1000A to 3000A is presented. Deposited films were annealed at 573K for one and half hour. The variations in the optical band gap were observed and showed decreasing behavior from 3.15 eV, 3.05 eV, from 3.18 eV to 3.10 eV and from 3.19 eV to 3.18 eV for films with respective thickness 1000A, 2000 A, 3000 A on increasing the evaporation rate from 5 As/sup-1/ to As/sup -1/ by keeping thickness constant. (author)

  18. Electrical, optical and photoelectric properties of cadmium sulfide monocrystals doped by indium and irradiated by electrons

    CERN Document Server

    Davidyuk, G E; Manzhara, V S

    2002-01-01

    One studied effect of irradiation by E = 1.2 MeV energy and PHI = 2 x 10 sup 1 sup 7 cm sup - sup 2 dose fast electrons on electrical, optical and photoelectrical CdS single-crystals doped by In. On the basis of analysis of the experimental results one makes conclusions about decomposition and, in this case, indium atoms occurring in cation sublattice nodes are knocked out by cadmium atoms. In CdS:In irradiated specimens one detected new centres of slow recombination with occurrence of maximums of photoconductivity optical suppression within lambda sub M sub sub 1 = 0.75 mu m and lambda sub M sub sub 2 = 1.03 mu m range. It is assumed that complexes containing cadmium vacancies and indium atoms are responsible for recombination new centres

  19. Electronic structure and optical properties of (BeTen/(ZnSem superlattices

    Directory of Open Access Journals (Sweden)

    Caid M.

    2016-03-01

    Full Text Available The structural, electronic and optical properties of (BeTen/(ZnSem superlattices have been computationally evaluated for different configurations with m = n and m≠n using the full-potential linear muffin-tin method. The exchange and correlation potentials are treated by the local density approximation (LDA. The ground state properties of (BeTen/(ZnSem binary compounds are determined and compared with the available data. It is found that the superlattice band gaps vary depending on the layers used. The optical constants, including the dielectric function ε(ω, the refractive index n(ω and the refractivity R(ω, are calculated for radiation energies up to 35 eV.

  20. The investigation of Ce doped ZnO crystal: The electronic, optical and magnetic properties

    Science.gov (United States)

    Wen, Jun-Qing; Zhang, Jian-Min; Qiu, Ze-Gang; Yang, Xu; Li, Zhi-Qin

    2018-04-01

    The electronic, optical and magnetic properties of Ce doped ZnO crystal have been studied by using first principles method. The research of formation energies show that Ce doped ZnO is energetically stable, and the formation energies reduce from 6.25% to 12.5% for Ce molar percentage. The energy band is still direct band gap after Ce doped, and band gap increases with the increase of Cesbnd Ce distance. The Fermi level moves upward into conduction band and the DOS moves to lower energy with the increase of Ce concentration, which showing the properties of n-type semiconductor. The calculated optical properties imply that Ce doped causes a red-shift of absorption peaks, and enhances the absorption of the visible light. The transition from ferromagnetic to antiferromagnetic has been found in Ce doped ZnO.

  1. 1st International Conference on Opto-Electronics and Applied Optics

    CERN Document Server

    Bhattacharya, Indrani

    2015-01-01

    The Proceedings of First International Conference on Opto-Electronics and Applied Optics 2014, IEM OPTRONIX 2014 presents the research contributions presented in the conference by researchers from both India and abroad. Contributions from established scientists as well as students are included. The book is organized to enable easy access to various topics of interest.   The first part includes the Keynote addresses by Phillip Russell, Max Planck Institute of the Light Sciences, Erlangen, Germany and Lorenzo Pavesi, University of Trento, Italy.   The second part focuses on the Plenary Talks given by eminent scientists, namely, Azizur Rahman, City University London, London; Bishnu Pal, President, The Optical Society of India; Kamakhya Ghatak, National Institute of Technology, Agartala; Kehar Singh, Former Professor, India Institute of Technology Delhi; Mourad Zghal, SUPCOM, University of Carthage, Tunisia; Partha Roy Chaudhuri, IIT Kharagpur; S K. Bhadra, CSIR-Central Glass and Ceramic Research Institute, Kol...

  2. Electron spin resonance of nitrogen-vacancy centers in optically trapped nanodiamonds

    Science.gov (United States)

    Horowitz, Viva R.; Alemán, Benjamín J.; Christle, David J.; Cleland, Andrew N.; Awschalom, David D.

    2012-01-01

    Using an optical tweezers apparatus, we demonstrate three-dimensional control of nanodiamonds in solution with simultaneous readout of ground-state electron-spin resonance (ESR) transitions in an ensemble of diamond nitrogen-vacancy color centers. Despite the motion and random orientation of nitrogen-vacancy centers suspended in the optical trap, we observe distinct peaks in the measured ESR spectra qualitatively similar to the same measurement in bulk. Accounting for the random dynamics, we model the ESR spectra observed in an externally applied magnetic field to enable dc magnetometry in solution. We estimate the dc magnetic field sensitivity based on variations in ESR line shapes to be approximately . This technique may provide a pathway for spin-based magnetic, electric, and thermal sensing in fluidic environments and biophysical systems inaccessible to existing scanning probe techniques. PMID:22869706

  3. Progress in studies of Electron-Cloud-Induced Optics Distortions at CESRTA

    International Nuclear Information System (INIS)

    Crittenden, J.A.; Calvey, J.R.; Dugan, G.F.; Kreinick, D.L.; Leong, Z.; Livezey, J.A.; Palmer, M.A.; Rubin, D.L.; Sagan, D.C.; Holtzapple, R.L.; Furman, M.A.; Penn, G.; Venturini, M.; Pivi, M.; Wang, L.; Harkay, K.

    2010-01-01

    The Cornell Electron Storage Ring Test Accelerator (CesrTA) program has included extensive measurements of coherent betatron tune shifts for a variety of electron and positron beam energies, bunch population levels, and bunch train configurations. The tune shifts have been shown to result primarily from the interaction of the beam with the space-charge field of the beam-induced low energy electron cloud in the vacuum chamber. Comparison to several advanced electron cloud simulation program packages has allowed determination of the sensitivity of these measurements to physical parameters characterizing the synchrotron radiation flux, the production of photoelectrons on the vacuum chamberwall, the beam emittance, lattice optics, and the secondary-electron yield model. We report on progress in understanding the cloud buildup and decay mechanisms in magnetic fields and in field-free regions, addressing quantitatively the precise determination of the physical parameters of the modeling. Validation of these models will serve as essential input in the design of damping rings for future high-energy linear colliders.

  4. Optical and electronic properties of InGaAs and nitride quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Baer, N.

    2006-06-15

    In the present thesis, the electronic and optical properties of such nanostructures have been investigated for the well established III-V and the new group-III nitride material system. The influence of Coulomb correlations on the optical spectra of InGaAs QDs are studied using a full configuration interaction approach. The resulting multi-exciton spectra for up to twelve excitons are investigated in detail. Characteristic features of the spectra are explained using simplified Hamiltonians that are derived taking into account the relative importance of various interaction contributions. Additionally, we study the electronic and optical properties of self-assembled InN/GaN quantum dots. The existence of an exactly degenerate p-shell is discussed in detail. Dipole and Coulomb matrix elements are calculated from these one-particle wave functions and serve as an input for configuration interaction calculations. We present multi-exciton emission spectra and investigate how Coulomb correlations and oscillator strengths are altered by the built-in electrostatic fields present in these structures. From our results, we predict vanishing exciton and biexciton ground state emission for small lens-shaped dots, which is explained by a careful analysis of the underlying symmetry group. To study the photoluminescence dynamics of an initially excited QD system, we employ a microscopic semiconductor theory. Carrier-carrier correlations beyond the Hartee-Fock level are included within a cluster expansion truncation scheme up to the singlet-doublet level. The influence of these correlations on the spectrum and the photoluminescence dynamics is investigated for the emission into free space as well as for QDs embedded in an optical microcavity. (orig.)

  5. Optical and electronic properties of InGaAs and nitride quantum dots

    International Nuclear Information System (INIS)

    Baer, N.

    2006-06-01

    In the present thesis, the electronic and optical properties of such nanostructures have been investigated for the well established III-V and the new group-III nitride material system. The influence of Coulomb correlations on the optical spectra of InGaAs QDs are studied using a full configuration interaction approach. The resulting multi-exciton spectra for up to twelve excitons are investigated in detail. Characteristic features of the spectra are explained using simplified Hamiltonians that are derived taking into account the relative importance of various interaction contributions. Additionally, we study the electronic and optical properties of self-assembled InN/GaN quantum dots. The existence of an exactly degenerate p-shell is discussed in detail. Dipole and Coulomb matrix elements are calculated from these one-particle wave functions and serve as an input for configuration interaction calculations. We present multi-exciton emission spectra and investigate how Coulomb correlations and oscillator strengths are altered by the built-in electrostatic fields present in these structures. From our results, we predict vanishing exciton and biexciton ground state emission for small lens-shaped dots, which is explained by a careful analysis of the underlying symmetry group. To study the photoluminescence dynamics of an initially excited QD system, we employ a microscopic semiconductor theory. Carrier-carrier correlations beyond the Hartee-Fock level are included within a cluster expansion truncation scheme up to the singlet-doublet level. The influence of these correlations on the spectrum and the photoluminescence dynamics is investigated for the emission into free space as well as for QDs embedded in an optical microcavity. (orig.)

  6. A Shocking Surprise in Stephan's Quintet

    Science.gov (United States)

    2006-01-01

    This false-color composite image of the Stephan's Quintet galaxy cluster clearly shows one of the largest shock waves ever seen (green arc). The wave was produced by one galaxy falling toward another at speeds of more than one million miles per hour. The image is made up of data from NASA's Spitzer Space Telescope and a ground-based telescope in Spain. Four of the five galaxies in this picture are involved in a violent collision, which has already stripped most of the hydrogen gas from the interiors of the galaxies. The centers of the galaxies appear as bright yellow-pink knots inside a blue haze of stars, and the galaxy producing all the turmoil, NGC7318b, is the left of two small bright regions in the middle right of the image. One galaxy, the large spiral at the bottom left of the image, is a foreground object and is not associated with the cluster. The titanic shock wave, larger than our own Milky Way galaxy, was detected by the ground-based telescope using visible-light wavelengths. It consists of hot hydrogen gas. As NGC7318b collides with gas spread throughout the cluster, atoms of hydrogen are heated in the shock wave, producing the green glow. Spitzer pointed its infrared spectrograph at the peak of this shock wave (middle of green glow) to learn more about its inner workings. This instrument breaks light apart into its basic components. Data from the instrument are referred to as spectra and are displayed as curving lines that indicate the amount of light coming at each specific wavelength. The Spitzer spectrum showed a strong infrared signature for incredibly turbulent gas made up of hydrogen molecules. This gas is caused when atoms of hydrogen rapidly pair-up to form molecules in the wake of the shock wave. Molecular hydrogen, unlike atomic hydrogen, gives off most of its energy through vibrations that emit in the infrared. This highly disturbed gas is the most turbulent molecular hydrogen ever seen. Astronomers were surprised not only by the turbulence

  7. Impact of Bulk Aggregation on the Electronic Structure of Streptocyanines: Implications for the Solid-State Nonlinear Optical Properties and All-Optical Switching Applications

    KAUST Repository

    Gieseking, Rebecca L.

    2014-10-16

    Polymethine dyes in dilute solutions show many of the electronic and optical properties required for all-optical switching applications. However, in the form of thin films, their aggregation and interactions with counterions do generally strongly limit their utility. Here, we present a theoretical approach combining molecular-dynamics simulations and quantum-chemical calculations to describe the bulk molecular packing of streptocyanines (taken as representative of simple polymethines) with counterions of different hardness (Cl and BPh4 ) and understand the impact on the optical properties. The accuracy of the force field we use is verified by reproducing experimental crystal parameters as well as the configurations of polymethine/counterion complexes obtained from electronic-structure calculations. The aggregation characteristics can be understood in terms of both polymethinecounterion and polymethinepolymethine interactions. The counterions are found to localize near one end of the streptocyanine backbones, and the streptocyanines form a broad range of aggregates with significant electronic couplings between neighboring molecules. As a consequence, the linear and nonlinear optical properties are substantially modified in the bulk. By providing an understanding of the relationship between the molecular interactions and the bulk optical properties, our results point to a clear strategy for designing polymethine and counterion molecular structures and optimizing the materials properties for all-optical switching applications.

  8. Impact of Bulk Aggregation on the Electronic Structure of Streptocyanines: Implications for the Solid-State Nonlinear Optical Properties and All-Optical Switching Applications

    KAUST Repository

    Gieseking, Rebecca L.; Mukhopadhyay, Sukrit; Shiring, Stephen B.; Risko, Chad; Bredas, Jean-Luc

    2014-01-01

    Polymethine dyes in dilute solutions show many of the electronic and optical properties required for all-optical switching applications. However, in the form of thin films, their aggregation and interactions with counterions do generally strongly limit their utility. Here, we present a theoretical approach combining molecular-dynamics simulations and quantum-chemical calculations to describe the bulk molecular packing of streptocyanines (taken as representative of simple polymethines) with counterions of different hardness (Cl and BPh4 ) and understand the impact on the optical properties. The accuracy of the force field we use is verified by reproducing experimental crystal parameters as well as the configurations of polymethine/counterion complexes obtained from electronic-structure calculations. The aggregation characteristics can be understood in terms of both polymethinecounterion and polymethinepolymethine interactions. The counterions are found to localize near one end of the streptocyanine backbones, and the streptocyanines form a broad range of aggregates with significant electronic couplings between neighboring molecules. As a consequence, the linear and nonlinear optical properties are substantially modified in the bulk. By providing an understanding of the relationship between the molecular interactions and the bulk optical properties, our results point to a clear strategy for designing polymethine and counterion molecular structures and optimizing the materials properties for all-optical switching applications.

  9. Feasibility of Optical Transition Radiation Imaging for Laser-driven Plasma Accelerator Electron-Beam Diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Lumpkin, A. H. [Fermilab; Rule, D. W. [Unlisted, US, MD; Downer, M. C. [Texas U.

    2017-10-09

    We report the initial considerations of using linearly polarized optical transition radiation (OTR) to characterize the electron beams of laser plasma accelerators (LPAs) such as at the Univ. of Texas at Austin. The two LPAs operate at 100 MeV and 2-GeV, and they currently have estimated normalized emittances at ~ 1-mm mrad regime with beam divergences less than 1/γ and beam sizes to be determined at the micron level. Analytical modeling results indicate the feasibility of using these OTR techniques for the LPA applications.

  10. Optical transitions and electronic interactions in self-assembled cobalt-fullerene mixture films

    Czech Academy of Sciences Publication Activity Database

    Lavrentiev, Vasyl; Chvostová, Dagmar; Lavrentieva, Inna; Vacík, Jiří; Daskal, Y.; Barchuk, M.; Rafaja, D.; Dejneka, Alexandr

    2017-01-01

    Roč. 50, č. 48 (2017), č. článku 485305. ISSN 0022-3727 R&D Projects: GA ČR(CZ) GBP108/12/G108; GA MŠk LM2015088; GA MŠk LM2015056 Institutional support: RVO:68378271 ; RVO:61389005 Keywords : fullerene * cobalt * electronic interaction * optical absorption * mixture film Subject RIV: BM - Solid Matter Physics ; Magnetism; BO - Biophysics (FZU-D) OBOR OECD: Condensed matter physics (including formerly solid state physics , supercond.); Biophysics (FZU-D) Impact factor: 2.588, year: 2016

  11. Structural, optical, and electronic studies of wide-bandgap lead halide perovskites

    KAUST Repository

    Comin, Riccardo; Walters, Grant; Thibau, Emmanuel Sol; Voznyy, Oleksandr; Lu, Zheng-Hong; Sargent, Edward H.

    2015-01-01

    © The Royal Society of Chemistry 2015. We investigate the family of mixed Br/Cl organolead halide perovskites which enable light emission in the blue-violet region of the visible spectrum. We report the structural, optical and electronic properties of this air-stable family of perovskites, demonstrating full bandgap tunability in the 400-550 nm range and enhanced exciton strength upon Cl substitution. We complement this study by tracking the evolution of the band levels across the gap, thereby providing a foundational framework for future optoelectronic applications of these materials.

  12. Electron mobility limited by optical phonons in wurtzite InGaN/GaN core-shell nanowires

    Science.gov (United States)

    Liu, W. H.; Qu, Y.; Ban, S. L.

    2017-09-01

    Based on the force-balance and energy-balance equations, the optical phonon-limited electron mobility in InxGa1-xN/GaN core-shell nanowires (CSNWs) is discussed. It is found that the electrons tend to distribute in the core of the CSNWs due to the strong quantum confinement. Thus, the scattering from first kind of the quasi-confined optical (CO) phonons is more important than that from the interface (IF) and propagating (PR) optical phonons. Ternary mixed crystal and size effects on the electron mobility are also investigated. The results show that the PR phonons exist while the IF phonons disappear when the indium composition x < 0.047, and vice versa. Accordingly, the total electron mobility μ first increases and then decreases with indium composition x, and reaches a peak value of approximately 3700 cm2/(V.s) when x = 0.047. The results also show that the mobility μ increases as increasing the core radius of CSNWs due to the weakened interaction between the electrons and CO phonons. The total electron mobility limited by the optical phonons exhibits an obvious enhancement as decreasing temperature or increasing line electron density. Our theoretical results are expected to be helpful to develop electronic devices based on CSNWs.

  13. First-principles calculations of structural, electronic and optical properties of CdxZn1-xS alloys

    KAUST Repository

    Noor, Naveed Ahmed; Ikram, Nazma; Ali, Sana Zulfiqar; Nazir, Safdar; Alay-E-Abbas, Syed Muhammad; Shaukat, Ali

    2010-01-01

    Structural, electronic and optical properties of ternary alloy system CdxZn1-xS have been studied using first-principles approach based on density functional theory. Electronic structure, density of states and energy band gap values for CdxZn1-xS

  14. The calculation of the electron structure and optical properties of TiNi martensite

    International Nuclear Information System (INIS)

    Kul'kova, S.E.; Beketov, K.A.; Egorushkin, V.E.; Muryzhnikova, O.N.

    1995-01-01

    The self-consistent calculation of NiTi B2 and B19' phases have been performed by the linear muffin-tin orbital method in atomic sphere approximation (LMTO-ASA). Two approaches for calculation of B2-phase band structure have been used and the essential differences in the Fermi surface have been pointed out. The alterations of NiTi electron characteristics at the martensitic transition have been analyzed. The optical spectra and their peculiarities in B2 and monoclinic B19' phases have been discussed. In the frames of first principles method electron-positron annihilation characteristics in B2-NiTi have been investigated too. It was shown that a rather satisfactory agreement with experimental results for NiTi was achieved. (orig.)

  15. Structural and Optical Changes of Poly-Vinylidene Fluoride by Electron Irradiation at High Dose Rate

    International Nuclear Information System (INIS)

    Jaleh, B.; Fakhri, P.; Borhani, M.; Habibi, S.; Noroozi, M.

    2012-01-01

    Poly-vinylidene fluoride films were prepared and irradiated by 10MeV electrons at different doses ranging from 50 to 300kGy with a dose rate of 10kGy/s. The FTIR results indicated that no major phase content change was observed. The optical absorption spectra indicated that the electron irradiation results in shifting of the absorption peak, appearance of a new peak and increasing the band gap (Eg). These changes may be due to the breaking of polymer chains and creation of new defects. The X-ray diffraction analysis of samples indicated that the crystallinity did not show any major changes. Concerning the gel fraction measurements, it was observed that gel fraction increases with increasing the dose, where it is an indication of the formation of cross-linked films.

  16. A computational study on the electronic and nonlinear optical properties of graphyne subunit

    Energy Technology Data Exchange (ETDEWEB)

    Bahat, Mehmet, E-mail: bahat@gazi.edu.tr; Güney, Merve Nurhan, E-mail: merveng87@gmail.com; Özbay, Akif, E-mail: aozbay@gazi.edu.tr [Department of Physics, Gazi University, Ankara, 06500 (Turkey)

    2016-03-25

    After discovery of graphene, it has been considered as basic material for the future nanoelectronic devices. Graphyne is a two- dimensional carbon allotropes as graphene which expected that its electronic properties is potentialy superior to graphene. The compound C{sub 24}H{sub 12} (tribenzocyclyne; TBC) is a substructure of graphyne. The electronic, and nonlinear optical properties of the C{sub 24}H{sub 12} and its some fluoro derivatives were calculated. The calculated properties are electric dipole moment, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies, polarizability and first hyperpolarizability. All calculations were performed at the B3LYP/6-31+G(d,p) level.

  17. Spectral evolution of soft x-ray emission from optically thin, high electron temperature platinum plasmas

    Directory of Open Access Journals (Sweden)

    Hiroyuki Hara

    2017-08-01

    Full Text Available The soft x-ray spectra of heavy element plasmas are frequently dominated by unresolved transition array (UTA emission. We describe the spectral evolution of an intense UTA under optically thin conditions in platinum plasmas. The UTA was observed to have a peak wavelength around 4.6 nm at line-of-sight averaged electron temperatures less than 1.4 keV at electron densities of (2.5–7.5 × 1013 cm−3. The UTA spectral structure was due to emission from 4d–4f transitions in highly charged ions with average charge states of q = 20–40. A numerical simulation successfully reproduced the observed spectral behavior.

  18. Further time-resolved electron-beam characterizations with optical transition radiation

    Energy Technology Data Exchange (ETDEWEB)

    Lumpkin, A.H. [Argonne National Lab., IL (United States). Advanced Photon Source Accelerator Systems Div.; Wilke, M.D. [Los Alamos National Lab., NM (United States)

    1992-12-31

    Time-resolved characterizations of electron beams using optical transition radiation (OTR) as a prompt conversion mechanism have recently been extended on the Los Alamos Free-electron Laser (FEL) facility 40-MeV linac. Two key timescales for rf-linac driven FELs are the micropulse (10 ps) and the macropulse (5 {mu}s to 1 ms). In the past we have used gated, intensified cameras to select a single or few micropulses (25 to 400 ns gate width) out of the pulse train to evaluate submacropulse effects. Recently, we have obtained some of the first measurements of micropulse bunch length (7 to 10 ps) and submacropulse spatialposition and profile using OTR and a Hamamatsu streak camera. Additionally, micropulse elongation effects and head-to-tail transverse kick effects are reported as a function of charge.

  19. Further time-resolved electron-beam characterizations with optical transition radiation

    Energy Technology Data Exchange (ETDEWEB)

    Lumpkin, A.H. (Argonne National Lab., IL (United States). Advanced Photon Source Accelerator Systems Div.); Wilke, M.D. (Los Alamos National Lab., NM (United States))

    1992-01-01

    Time-resolved characterizations of electron beams using optical transition radiation (OTR) as a prompt conversion mechanism have recently been extended on the Los Alamos Free-electron Laser (FEL) facility 40-MeV linac. Two key timescales for rf-linac driven FELs are the micropulse (10 ps) and the macropulse (5 [mu]s to 1 ms). In the past we have used gated, intensified cameras to select a single or few micropulses (25 to 400 ns gate width) out of the pulse train to evaluate submacropulse effects. Recently, we have obtained some of the first measurements of micropulse bunch length (7 to 10 ps) and submacropulse spatialposition and profile using OTR and a Hamamatsu streak camera. Additionally, micropulse elongation effects and head-to-tail transverse kick effects are reported as a function of charge.

  20. Time-resolved electron-beam characterizations with optical transition radiation

    Energy Technology Data Exchange (ETDEWEB)

    Lumpkin, A.H. (Argonne National Lab., IL (United States)); Wilke, M.D. (Los Alamos National Lab., NM (United States))

    1992-01-01

    Time-resolved characterizations of electron beams using optical transition radiation (OTR) as a prompt conversion mechanism have recently been extended on the Los Alamos Free-electron Laser (FEL) facility 40-MeV linac. Two key timescales for rf-linac driven FELs are the micropulse (10 ps) and the macropulse (5 {mu}s to 1 ms). In the past we have used gated, intensified cameras to select a single or few micropulses (25 to 400 ns gate width) out of the pulse train to evaluate submacropulse effects. Recently, we have obtained some of the first measurements of micropulse bunch length (7 to 10 ps) and submacropulse spatial position and profile using OTR and a Hamamatsu streak camera. Additionally, micropulse elongation effects and head-to-tail transverse kicks are reported as a function of charge.

  1. Time-resolved electron-beam characterizations with optical transition radiation

    Energy Technology Data Exchange (ETDEWEB)

    Lumpkin, A.H. [Argonne National Lab., IL (United States); Wilke, M.D. [Los Alamos National Lab., NM (United States)

    1992-09-01

    Time-resolved characterizations of electron beams using optical transition radiation (OTR) as a prompt conversion mechanism have recently been extended on the Los Alamos Free-electron Laser (FEL) facility 40-MeV linac. Two key timescales for rf-linac driven FELs are the micropulse (10 ps) and the macropulse (5 {mu}s to 1 ms). In the past we have used gated, intensified cameras to select a single or few micropulses (25 to 400 ns gate width) out of the pulse train to evaluate submacropulse effects. Recently, we have obtained some of the first measurements of micropulse bunch length (7 to 10 ps) and submacropulse spatial position and profile using OTR and a Hamamatsu streak camera. Additionally, micropulse elongation effects and head-to-tail transverse kicks are reported as a function of charge.

  2. Electronic structure and optical properties of the thiolate-protected Au28(SMe)20 cluster.

    Science.gov (United States)

    Knoppe, Stefan; Malola, Sami; Lehtovaara, Lauri; Bürgi, Thomas; Häkkinen, Hannu

    2013-10-10

    The recently reported crystal structure of the Au28(TBBT)20 cluster (TBBT: p-tert-butylbenzenethiolate) is analyzed with (time-dependent) density functional theory (TD-DFT). Bader charge analysis reveals a novel trimeric Au3(SR)4 binding motif. The cluster can be formulated as Au14(Au2(SR)3)4(Au3(SR)4)2. The electronic structure of the Au14(6+) core and the ligand-protected cluster were analyzed, and their stability can be explained by formation of distorted eight-electron superatoms. Optical absorption and circular dichroism (CD) spectra were calculated and compared to the experiment. Assignment of handedness of the intrinsically chiral cluster is possible.

  3. A Simple Metric for Determining Resolution in Optical, Ion, and Electron Microscope Images.

    Science.gov (United States)

    Curtin, Alexandra E; Skinner, Ryan; Sanders, Aric W

    2015-06-01

    A resolution metric intended for resolution analysis of arbitrary spatially calibrated images is presented. By fitting a simple sigmoidal function to pixel intensities across slices of an image taken perpendicular to light-dark edges, the mean distance over which the light-dark transition occurs can be determined. A fixed multiple of this characteristic distance is then reported as the image resolution. The prefactor is determined by analysis of scanning transmission electron microscope high-angle annular dark field images of Si. This metric has been applied to optical, scanning electron microscope, and helium ion microscope images. This method provides quantitative feedback about image resolution, independent of the tool on which the data were collected. In addition, our analysis provides a nonarbitrary and self-consistent framework that any end user can utilize to evaluate the resolution of multiple microscopes from any vendor using the same metric.

  4. Intense source of spin-polarized electrons using laser-induced optical pumping

    International Nuclear Information System (INIS)

    Gray, L.G.; Giberson, K.W.; Cheng, C.; Keiffer, R.S.; Dunning, F.B.; Walters, G.K.

    1983-01-01

    A source of spin-polarized electrons based on a laser-pumped flowing helium afterglow is described. He(2 3 S) atoms contained in the afterglow are optically pumped using circularly polarized 1.08-μm (2 3 S→2 3 P) radiation provided by a NaF (F 2+ )( color-center laser. Spin angular momentum conservation in subsequent chemi-ionization reactions with CO 2 produces polarized electrons that are extracted from the afterglow. At low currents, < or approx. =1 μA, polarizations of approx.70%--80% are achieved. At higher currents the polarization decreases, falling to approx.40% at 50 μA. The spin polarization can be simply reversed (P→-P) and the source is suitable for use in the majority of low-energy spin-dependent scattering experiments proposed to date

  5. Laser based analysis using a passively Q-switched laser employing analysis electronics and a means for detecting atomic optical emission of the laser media

    Science.gov (United States)

    Woodruff, Steven D.; Mcintyre, Dustin L.

    2016-03-29

    A device for Laser based Analysis using a Passively Q-Switched Laser comprising an optical pumping source optically connected to a laser media. The laser media and a Q-switch are positioned between and optically connected to a high reflectivity mirror (HR) and an output coupler (OC) along an optical axis. The output coupler (OC) is optically connected to the output lens along the optical axis. A means for detecting atomic optical emission comprises a filter and a light detector. The optical filter is optically connected to the laser media and the optical detector. A control system is connected to the optical detector and the analysis electronics. The analysis electronics are optically connected to the output lens. The detection of the large scale laser output production triggers the control system to initiate the precise timing and data collection from the detector and analysis.

  6. Optical network and FPGA/DSP based control system for free electron laser

    International Nuclear Information System (INIS)

    Romaniuk, R.S.; Pozniak, K.T.; Czarski, T.; Czuba, K.; Giergusiewicz, W.; Kasprowicz, G.; Koprek, W.

    2005-01-01

    The work presents a structural and functional model of a distributed low level radio frequency (LLRF) control, diagnostic and telemetric system for a large industrial object. An example of system implementation is the European TESLA-XFEL accelerator. The free electron laser is expected to work in the VUV region now and in the range of X-rays in the future. The design of a system based on the FPGA circuits and multi-gigabit optical network is discussed. The system design approach is fully parametric. The major emphasis is put on the methods of the functional and hardware concentration to use fully both: a very big transmission capacity of the optical fiber telemetric channels and very big processing power of the latest series of DSP/PC enhanced and optical I/O equipped, FPGA chips. The subject of the work is the design of a universal, laboratory module of the LLRF sub-system. The current parameters of the system model, under the design, are presented. The considerations are shown on the background of the system application in the hostile industrial environment. The work is a digest of a few development threads of the hybrid, optoelectronic, telemetric networks (HOTN). In particular, the outline of construction theory of HOTN node was presented as well as the technology of complex, modular, multilayer HOTN system PCBs. The PCBs contain critical sub-systems of the node and the network. The presented exemplary sub-systems are: fast optical data transmission of 2.5 Gbit/s, 3.125 Gbit/s and 10 Gbit/s; fast A/C and C/A multichannel data conversion managed by FPGA chip (40 MHz, 65 MHz, 105 MHz), data and functionality concentration, integration of floating point calculations in the DSP units of FPGA circuit, using now discrete and next integrated PC chip with embedded OS; optical distributed timing system of phase reference; and 1GbEth video interface (over UTP or FX) for CCD telemetry and monitoring. The data and functions concentration in the HOTN node is necessary to

  7. Peculiarity of electron optical orientation in Hg1-xMnxTe and Hg1-xCdxTe alloys

    International Nuclear Information System (INIS)

    Georgitseh, E.I.; Ivanov-Omskij, V.I.; Pogorletskij, V.M.

    1991-01-01

    To clarify the effect of exchange interaction of electrons with manganese ions on electron spin relaxation, a study was made on optical orientation in Hg 1-x Mn x Te alloy and Hg 1-x Cd x Te alloys with similar parameters of energy spectrum at 4.2 K. It is shown that exchange interaction in semimagnetic Hg 1-x Mn x Te solutions, caused by the presence of manganese ions, reduced the time of spin relaxation. However, this reduction is not sufficient make optical orientation of electrons not observable

  8. Interband optical absorption in the Wannier-Stark ladder under the electron-LO-phonon resonance condition

    International Nuclear Information System (INIS)

    Govorov, A.O.

    1993-08-01

    Interband optical absorption in the Wannier-Stark ladder in the presence of the electron-LO-phonon resonance is investigated theoretically. The electron-LO-phonon resonance occurs when the energy spacing between adjacent Stark-ladder levels coincides with the LO-phonon energy. We propose a model describing the polaron effect in a superlattice. Calculations show that the absorption line shape is strongly modified due to the polaron effect under the electron-LO-phonon resonance condition. We consider optical phenomena in a normal magnetic field that leads to enhancement of polaron effects. (author). 17 refs, 5 figs

  9. Surprise: Dwarf Galaxy Harbors Supermassive Black Hole

    Science.gov (United States)

    2011-01-01

    The surprising discovery of a supermassive black hole in a small nearby galaxy has given astronomers a tantalizing look at how black holes and galaxies may have grown in the early history of the Universe. Finding a black hole a million times more massive than the Sun in a star-forming dwarf galaxy is a strong indication that supermassive black holes formed before the buildup of galaxies, the astronomers said. The galaxy, called Henize 2-10, 30 million light-years from Earth, has been studied for years, and is forming stars very rapidly. Irregularly shaped and about 3,000 light-years across (compared to 100,000 for our own Milky Way), it resembles what scientists think were some of the first galaxies to form in the early Universe. "This galaxy gives us important clues about a very early phase of galaxy evolution that has not been observed before," said Amy Reines, a Ph.D. candidate at the University of Virginia. Supermassive black holes lie at the cores of all "full-sized" galaxies. In the nearby Universe, there is a direct relationship -- a constant ratio -- between the masses of the black holes and that of the central "bulges" of the galaxies, leading them to conclude that the black holes and bulges affected each others' growth. Two years ago, an international team of astronomers found that black holes in young galaxies in the early Universe were more massive than this ratio would indicate. This, they said, was strong evidence that black holes developed before their surrounding galaxies. "Now, we have found a dwarf galaxy with no bulge at all, yet it has a supermassive black hole. This greatly strengthens the case for the black holes developing first, before the galaxy's bulge is formed," Reines said. Reines, along with Gregory Sivakoff and Kelsey Johnson of the University of Virginia and the National Radio Astronomy Observatory (NRAO), and Crystal Brogan of the NRAO, observed Henize 2-10 with the National Science Foundation's Very Large Array radio telescope and

  10. Electron acceleration in laser-plasma interaction: development and characterization of an optical injector

    International Nuclear Information System (INIS)

    Rechatin, C.

    2009-09-01

    In any particle accelerator, the injector plays a crucial role since it determines most of the characteristics of the accelerated beam. This is also true for laser-plasma accelerators, that are based on the interaction of an ultra short, ultra intense laser with an underdense plasma. However, due to the compactness of these accelerators, injection is a real challenge: to obtain a good beam quality, injected electron beams have to be ultra short and precisely synchronized with the laser. In this manuscript, the relevance of an optical injector, that relies on a second laser pulse, is experimentally demonstrated. With this injector, mono energetic electron beams have been produced in a stable manner. Moreover, this injector gives control over the electron beam parameters. Using the parameters of the second laser pulse, it has been proven that the energy, the charge and the energy spread of the accelerated beam can be simply tuned. Those additional controls make it possible to study in great details the physical phenomena at play during the acceleration. Beam loading effects, due to the interaction of the accelerated bunch with the plasma, have been identified and studied. With optimized injector parameters, the narrowest electron beams measured to date in the laser plasma interaction have been obtained, with a relative energy spread of 1%. (author)

  11. Electronic structure of antiferromagnetic UN and UPtGe single crystals from optical and magneto-optical spectroscopy

    International Nuclear Information System (INIS)

    Marutzky, M.

    2006-01-01

    In this thesis the study of the magneto-optical Kerr effect and the determination of the optical constants by means of ellipsometry and Fourier-transformation infrared spectroscopy of UN and UPtGe is described. In UPtGe an optical anisotropy was detected over a spectral range from 6 meV to 32 eV. (HSI)

  12. Optical properties and electronic transitions of DNA oligonucleotides as a function of composition and stacking sequence.

    Science.gov (United States)

    Schimelman, Jacob B; Dryden, Daniel M; Poudel, Lokendra; Krawiec, Katherine E; Ma, Yingfang; Podgornik, Rudolf; Parsegian, V Adrian; Denoyer, Linda K; Ching, Wai-Yim; Steinmetz, Nicole F; French, Roger H

    2015-02-14

    The role of base pair composition and stacking sequence in the optical properties and electronic transitions of DNA is of fundamental interest. We present and compare the optical properties of DNA oligonucleotides (AT)10, (AT)5(GC)5, and (AT-GC)5 using both ab initio methods and UV-vis molar absorbance measurements. Our data indicate a strong dependence of both the position and intensity of UV absorbance features on oligonucleotide composition and stacking sequence. The partial densities of states for each oligonucleotide indicate that the valence band edge arises from a feature associated with the PO4(3-) complex anion, and the conduction band edge arises from anti-bonding states in DNA base pairs. The results show a strong correspondence between the ab initio and experimentally determined optical properties. These results highlight the benefit of full spectral analysis of DNA, as opposed to reductive methods that consider only the 260 nm absorbance (A260) or simple purity ratios, such as A260/A230 or A260/A280, and suggest that the slope of the absorption edge onset may provide a useful metric for the degree of base pair stacking in DNA. These insights may prove useful for applications in biology, bioelectronics, and mesoscale self-assembly.

  13. Development of an optical character recognition pipeline for handwritten form fields from an electronic health record.

    Science.gov (United States)

    Rasmussen, Luke V; Peissig, Peggy L; McCarty, Catherine A; Starren, Justin

    2012-06-01

    Although the penetration of electronic health records is increasing rapidly, much of the historical medical record is only available in handwritten notes and forms, which require labor-intensive, human chart abstraction for some clinical research. The few previous studies on automated extraction of data from these handwritten notes have focused on monolithic, custom-developed recognition systems or third-party systems that require proprietary forms. We present an optical character recognition processing pipeline, which leverages the capabilities of existing third-party optical character recognition engines, and provides the flexibility offered by a modular custom-developed system. The system was configured and run on a selected set of form fields extracted from a corpus of handwritten ophthalmology forms. The processing pipeline allowed multiple configurations to be run, with the optimal configuration consisting of the Nuance and LEADTOOLS engines running in parallel with a positive predictive value of 94.6% and a sensitivity of 13.5%. While limitations exist, preliminary experience from this project yielded insights on the generalizability and applicability of integrating multiple, inexpensive general-purpose third-party optical character recognition engines in a modular pipeline.

  14. Electronic, optical, infrared, and elastic properties of KCdCO3F from first principles

    Science.gov (United States)

    Huang, Xue-Qian; Xue, Han-Yu; Zhang, Can; Pang, Dong-Dong; Lv, Zhen-Long; Duan, Man-Yi

    2018-05-01

    KCdCO3F is a newly synthesized promising ultraviolet nonlinear optical crystal, but its structure is disputed and its fundamental properties have not been well studied. Here our first-principles study indicates that the structure with the space group P 6 bar c2 is energetically more stable than the P 6 bar m2 phase. We systematically investigated its electronic, optical, vibrational, infrared, and elastic properties. The results reveal that KCdCO3F is a direct-band-gap insulator with rather flat bands below the Fermi level. Analyses of its partial density of states revealed that the top (bottom) of its valence (conduction) band is formed by the O 2p (Cd 5s) orbital. It is a negative uniaxial crystal with ionic-covalent nature. Both infrared-active and Raman-active modes exist at its Brillouin zone center, and ions contribute more to its static dielectric constants. Its optical spectra in the visual and infrared ranges were studied, and their origins were revealed. Calculations indicate that KCdCO3F is mechanically stable but anisotropic since it is more vulnerable to shear stress and is easy to cleave along the c axis.

  15. The electronic and optical properties of germanium tellurite glasses containing various transition metal oxides

    International Nuclear Information System (INIS)

    Khan, M.N.

    1988-01-01

    Various transition metal oxides, such as TiO 2 , V 2 O 5 , NiO, CuO, and ZnO are added to germanium-tellurite glass and measurements are reported of the electrical conductivity, density, optical absorption, infra-red absorption spectra, and electron spin resonance. It is found that the d.c. conductivity of glasses containing the same amount of V 2 O 5 is higher than that of germanium tellurite glasses containing a similar amount of other transition metal oxides, and is due to hopping between localized states. The optical absorption measurements show that the fundamental absorption edge is a function of glass composition and the optical absorption is due to forbidden indirect transitions. From the infra-red absorption spectra, it is found that the addition of transition metal oxides does not introduce any new absorption band in the infra-red spectrum of germanium tellurite glasses. A small shift of existing absorptions toward higher wave number is observed. The ESR measurements revealed that some transition metal ions are diamagnetic while others are paramagnetic in the glass network. (author)

  16. Microscopic kinetic analysis of space-charge induced optical microbunching in a relativistic electron beam

    Directory of Open Access Journals (Sweden)

    Agostino Marinelli

    2010-11-01

    Full Text Available Longitudinal space-charge forces from density fluctuations generated by shot noise can be a major source of microbunching instability in relativistic high brightness electron beams. The gain in microbunching due to this effect is broadband, extending at least up to optical frequencies, where the induced structure on the beam distribution gives rise to effects such as coherent optical transition radiation. In the high-frequency regime, theoretical and computational analyses of microbunching formation require a full three-dimensional treatment. In this paper we address the problem of space-charge induced optical microbunching formation in the high-frequency limit when transverse thermal motion due to finite emittance is included for the first time. We derive an analytical description of this process based on the beam’s plasma dielectric function. We discuss the effect of transverse temperature on the angular distribution of microbunching gain and its connection to the physics of Landau damping in longitudinal plasma oscillations. Application of the theory to a relevant experimental scenario is discussed. The analytical results obtained are then compared to the predictions arising from high resolution three-dimensional molecular dynamics simulations.

  17. Optical potential approach to the electron-atom impact ionization threshold problem

    Science.gov (United States)

    Temkin, A.; Hahn, Y.

    1973-01-01

    The problem of the threshold law for electron-atom impact ionization is reconsidered as an extrapolation of inelastic cross sections through the ionization threshold. The cross sections are evaluated from a distorted wave matrix element, the final state of which describes the scattering from the Nth excited state of the target atom. The actual calculation is carried for the e-H system, and a model is introduced which is shown to preserve the essential properties of the problem while at the same time reducing the dimensionability of the Schrodinger equation. Nevertheless, the scattering equation is still very complex. It is dominated by the optical potential which is expanded in terms of eigen-spectrum of QHQ. It is shown by actual calculation that the lower eigenvalues of this spectrum descend below the relevant inelastic thresholds; it follows rigorously that the optical potential contains repulsive terms. Analytical solutions of the final state wave function are obtained with several approximations of the optical potential.

  18. Electronic, elastic, acoustic and optical properties of cubic TiO2: A DFT approach

    International Nuclear Information System (INIS)

    Mahmood, Tariq; Cao, Chuanbao; Tahir, Muhammad; Idrees, Faryal; Ahmed, Maqsood; Tanveer, M.; Aslam, Imran; Usman, Zahid; Ali, Zulfiqar; Hussain, Sajad

    2013-01-01

    The electronic, elastic, acoustic and optical properties of cubic phases TiO 2 fluorite and pyrite are investigated using the first principles calculations. We have employed five different exchange–correlation functions within the local density and generalized gradient approximations using the ultrasoft plane wave pseudopotential method. The calculated band structures of cubic-TiO 2 elucidate that the TiO 2 fluorite and pyrite are direct and indirect semiconductors in contrast to the previous findings. From our studied properties such as bulk and shear moduli, elastic constants C 44 and Debye temperature for TiO 2 fluorite and pyrite, we infer that both the cubic phases are not superhard materials and the pyrite phase is harder than fluorite. The longitudinal and transversal acoustic wave speeds for both phases in the directions [100], [110] and [111] are determined using the pre-calculated elastic constants. In addition, we also calculate the optical properties such as dielectric function, absorption spectrum, refractive index and energy loss function using the pre-optimized structure. On the observation of optical properties TiO 2 fluorite phase turn out to be more photocatalytic than pyrite

  19. Ultrafast optical pump terahertz-probe spectroscopy of strongly correlated electron materials

    International Nuclear Information System (INIS)

    Averitt, R.D.; Taylor, Antoinette J.; Thorsmolle, V.K.; Jia, Quanxi; Lobad, A.I.; Trugman, S.A.

    2001-01-01

    We have used optical-pump far-infrared probe spectroscopy to probe the low energy electron dynamics of high temperature superconductors and colossal magnetoresistance manganites. For the superconductor YBa2Cu3O7, picosecond conductivity measurements probe the interplay between Cooper-pairs and quasiparticles. In optimally doped films, the recovery time for long-range phase-coherent pairing increases from ∼1.5 ps at 4K to ∼3.5 ps near Tc, consistent with the closing of the superconducting gap. For underdoped films, the measured recovery time is temperature independent (3.5 ps) in accordance with the presence of a pseudogap. Ultrafast picosecond measurements of optically induced changes in the absolute conductivity of La0:7M0:3MnO3 thin films (M = Ca, Sr) from 10K to ∼0.9Tc reveal a two-component relaxation. A fast, ∼2 ps, conductivity decrease arises from optically induced modification of the effective phonon temperature. The slower component, related to spin-lattice relaxation, has a lifetime that increases upon approaching Tc from below in accordance with an increasing spin specific heat. Our results indicate that for T<< Tc, the conductivity is determined by incoherent phonons while spin fluctuations dominate near Tc.

  20. Electronic and optical properties of bilayer PbI2: a first-principles study

    Science.gov (United States)

    Shen, Chenhai; Wang, Guangtao

    2018-01-01

    By employing first-principles methods, we investigate the effects of stacking patterns and interlayer coupling on the electronic structures and optical properties of bilayer (BL) PbI2. For optical properties, excitonic effects are considered. The results show that crystal-type BL PbI2 stacking pattern is the most stable bilayer structures with the equilibrium interlayer distance of 3.27 Å and a direct band structure. Moreover, for all considered patterns, the interlayer coupling can induce the band structures to transform from indirect to direct and also the band gap values to vary from 2.56 eV to 2.62 eV. In addition, our calculations show that the exciton binding energy of the most stable pattern is 0.81 eV, and excitonic effects have obvious influences on optical responses of BL PbI2. These results may be useful to future experimental studies on optoelectronic properties of two-dimensional BL PbI2 nanosheets.

  1. Electronic band structure and optical properties of the cubic, Sc, Y and La hydride systems

    International Nuclear Information System (INIS)

    Peterman, D.J.

    1980-01-01

    Electronic band structure calculations are used to interpret the optical spectra of the cubic Sc, Y and La hydride systems. Self-consistent band calculations of ScH 2 and YH 2 were carried out. The respective joint densities of states are computed and compared to the dielectric functions determined from the optical measurements. Additional calculations were performed in which the Fermi level or band gap energies are rigidly shifted by a small energy increment. These calculations are then used to simulate the derivative structure in thermomodulation spectra and relate the origin of experimental interband features to the calculated energy bands. While good systematic agreement is obtained for several spectral features, the origin of low-energy interband transitions in YH 2 cannot be explained by these calculated bands. A lattice-size-dependent premature occupation of octahedral sites by hydrogen atoms in the fcc metal lattice is suggested to account for this discrepancy. Various non-self-consistent calculations are used to examine the effect of such a premature occupation. Measurements of the optical absorptivity of LaH/sub x/ with 1.6 2 lattice. These experimental results also suggest that, in contrast to recent calculations, LaH 3 is a small-band-gap semiconductor

  2. Entanglement purification and concentration of electron-spin entangled states using quantum-dot spins in optical microcavities

    International Nuclear Information System (INIS)

    Wang Chuan; Zhang Yong; Jin Guangsheng

    2011-01-01

    We present an entanglement purification protocol and an entanglement concentration protocol for electron-spin entangled states, resorting to quantum-dot spin and optical-microcavity-coupled systems. The parity-check gates (PCGs) constructed by the cavity-spin-coupling system provide a different method for the entanglement purification of electron-spin entangled states. This protocol can efficiently purify an electron ensemble in a mixed entangled state. The PCGs can also concentrate electron-spin pairs in less-entangled pure states efficiently. The proposed methods are more flexible as only single-photon detection and single-electron detection are needed.

  3. Effect of phosphorus on the electronic and optical properties of naphthoxaphospholes: theoretical investigation

    Science.gov (United States)

    Moon, Jiwon; Kim, Minbi; Lim, Jeong Sik; Kim, Joonghan

    2018-06-01

    Density functional theory (DFT) and time-dependent DFT calculations were performed to elucidate the electronic and optical properties of 2-R-naphthol[2,3-d]oxaphospholes (R-NOPs). On the basis of the calculated results, the poor π overlap between the 3pz orbital of P atom and the 2pz orbitals of other atoms and increasing polarity of P atom result in a reduced energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital. When these two effects are considered simultaneously, the absorption energies obtained for the S1 state can be below 3.00 eV according to replace the P atom of oxaphosphole ring by As atom (increasing the poor π overlap) and change the functional groups (increasing polarity). The origin of these two effects is the inherent size of the 3p orbital of P atom. The role of P atom in the control of the electronic and optical properties of R-NOPs is clearly elucidated.

  4. The study of electronic structures and optical properties of Al-doped GaN

    International Nuclear Information System (INIS)

    Li Enling; Hou Liping; Liu Mancang; Xi Meng; Wang Xiqiang; Dai Yuanbin; Li Lisha

    2011-01-01

    The electronic structures and optical properties of undoped and Al-doped GaN (Al x Ga 1-x N, x=0.0625, 0.125, 0.25) have been studied based on generalized gradient approximation (GGA) method of density functional theory (DFT). The differences of the electronic structures and optical properties of undoped and Al-doped GaN have been discussed in detail. The result shows: according to total density of state of undoped and Al-doped GaN, the conduction band becomes width and moves to high energy level with gradual increase concentration of Al impurity. Impurity energy band isn't found in energy band structures of Al x Ga 1-x N, the same as energy band structures of undoped GaN, but the band gaps gradually become wide with increase of Al impurity. Absorption spectra of undoped and Al-doped GaN of main absorption peak moves to high energy level with increase of Al impurity.

  5. Structural, electronic, linear, and nonlinear optical properties of ZnCdTe{sub 2} chalcopyrite

    Energy Technology Data Exchange (ETDEWEB)

    Ouahrani, Tarik [Laboratoire de Physique Theorique, Universite de Tlemcen, B.P. 230, Tlemcen 13000 (Algeria); Reshak, Ali H. [Institute of Physical Biology, South Bohemia University, Nove Hrady 37333 (Czech Republic); School of Microelectronic Engineering, University of Malaysia Perlis (UniMAP), Block A, Kompleks Pusat Pengajian, 02600 Arau Jejawi, Perlis (Malaysia); Khenata, R. [Laboratoire de Physique Quantique et de Modelisation Mathematique, Universite de Mascara, Mascara 29000 (Algeria); Department of Physics and Astronomy, Faculty of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia); Baltache, H.; Amrani, B. [Laboratoire de Physique Quantique et de Modelisation Mathematique, Universite de Mascara, Mascara 29000 (Algeria); Bouhemadou, A. [Department of Physics and Astronomy, Faculty of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia); Faculty of Sciences, Department of Physics, University of Setif, Setif 19000 (Algeria)

    2011-03-15

    We report results of first-principles density functional calculations using the full-potential linearized augmented plane wave method. The generalized gradient approximation (GGA) and the Engel-Vosko-GGA (EV-GGA) formalism were used for the exchange-correlation energy to calculate the structural, electronic, linear, and nonlinear optical properties of the chalcopyrite ZnCdTe{sub 2} compound. The valence band maximum and the conduction band minimum are located at the {gamma}-point, resulting in a direct band gap of about 0.71 eV for GGA and 1.29 eV for EV-GGA. The results of bulk properties, such as lattice parameters (a, c, and u), bulk modulus B, and its pressure derivative B' are evaluated. The optical properties of this compound, namely the real and the imaginary parts of the dielectric function, reflectivity, and refractive index, show a considerable anisotropy as a consequence ZnCdTe{sub 2} posseses a strong birefringence. In addition, the extinction coefficient, the electron energy loss function, and the nonlinear susceptibility are calculated and their spectra are analyzed. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Electronic excitation induced modifications of optical and morphological properties of PCBM thin films

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, T. [Department of Physics and Materials Research Centre, Malaviya National Institute of Technology, Jaipur 302017 (India); Singhal, R., E-mail: rsinghal.phy@mnit.ac.in [Department of Physics and Materials Research Centre, Malaviya National Institute of Technology, Jaipur 302017 (India); Vishnoi, R. [Department of Physics and Materials Research Centre, Malaviya National Institute of Technology, Jaipur 302017 (India); Department of Physics, Vardhman (P.G.) College, Bijnor 246701, U.P. (India); Sharma, P. [Department of Physics and Materials Research Centre, Malaviya National Institute of Technology, Jaipur 302017 (India); Patra, A.; Chand, S. [National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Lakshmi, G.B.V.S. [Inter University Accelerator Centre, Post Box No. 10502, New Delhi 110067 (India); Biswas, S.K. [Department of Metallurgical and Materials Engineering, Malaviya National Institute of Technology, Jaipur 302017 (India)

    2016-07-15

    Highlights: • Spin casted PCBM thin films are irradiated by 90 MeV Ni{sup 7+} ion beam. • The decrease in band gap was found after irradiation. • There is a decomposition of molecular bond due to ion irradiation. • Roughness is also found to be dependent on incident ion fluence. - Abstract: Phenyl C{sub 61} butyric acid methyl ester (PCBM) is a fullerene derivative and most commonly used in organic photovoltaic devices both as electron acceptor and transporting material due to high electron mobility. PCBM is easy to spin caste on some substrate as it is soluble in chlorobenzene. In this study, the spin coated thin films of PCBM (on two different substrate, glass and double sided silicon) were irradiated using 90 MeV Ni{sup 7+} swift heavy ion beam at low fluences ranging from 1 × 10{sup 9} to 1 × 10{sup 11} ions/cm{sup 2} to study the effect of ion beam irradiation. The pristine and irradiated PCBM thin films were characterized by UV–visible absorption spectroscopy and fourier transform infrared spectroscopy (FTIR) to investigate the optical properties before and after irradiation. These thin films were further analyzed using atomic force microscopy (AFM) to investigate the morphological modifications which are induced by energetic ions. The variation in optical band gap after irradiation was measured using Tauc’s relation from UV–visible absorption spectra. A considerable change was observed with increasing fluence in optical band gap of irradiated thin films of PCBM with respect to the pristine film. The decrease in FTIR band intensity of C{sub 60} cage reveals the polymerization reaction due to high energy ion impact. The roughness is also found to be dependent on incident fluences. This study throws light for the application of PCBM in organic solar cells in form of ion irradiation induced nanowires of PCBM for efficient charge carrier transportation in active layer.

  7. Numerical studies on the electro-optic detection of femtosecond electron bunches

    Directory of Open Access Journals (Sweden)

    S. Casalbuoni

    2008-07-01

    Full Text Available The electro-optic (EO effect is a powerful diagnostic tool for determining the time profile of ultrashort relativistic electron bunches. When a relativistic bunch passes within a few mm of an electro-optic crystal, its transient electric field is equivalent to a half-cycle THz pulse passing through the crystal. The induced birefringence can be detected with polarized femtosecond laser pulses. A simulation code has been written in order to understand the faithfulness and the limitations of electron bunch shape reconstruction by EO sampling. The THz pulse and the laser pulse are propagated as wave packets through the EO crystal. Alternatively, the response function method is applied. Using experimental data on the material properties of zinc telluride (ZnTe and gallium phosphide (GaP, the effects of velocity mismatch, pulse shape distortion, and signal broadening are explicitly taken into account. The simulations show that the most severe limitation on the time resolution is given by the transverse-optical (TO lattice oscillation in the EO crystal. The lowest TO frequency is 5.3 THz in ZnTe and 11 THz in GaP. Only the Fourier components below the TO resonance are usable for the bunch shape reconstruction. This implies that the shortest rms bunch length which can be resolved with moderate distortion amounts to σ≈90  fs in ZnTe and σ≈50  fs in GaP. The influence of the crystal thickness on the amplitude and width of the EO signal is studied. The optimum thickness is in the range from 100 to 300  μm for ZnTe and from 50 to 100  μm for GaP.

  8. Electronic structure, Fermi surface and optical properties of metallic compound Be8(B48)B2

    International Nuclear Information System (INIS)

    Reshak, A.H.; Azam, Sikander; Alahmed, Z.A.; Chyský, Jan

    2014-01-01

    The band structure, density of states, electronic charge density, Fermi surface and optical properties for B 8 (Be 48 )B 2 compound has been investigated in the support of density functional theory (DFT). The atomic positions of B 8 (Be 48 )B 2 compound were optimized by minimization of the forces acting on the atoms using the full potential linear augmented plane wave (FPLAPW) method. We have employed the local density approximation (LDA), generalized gradient approximation (GGA) and Engal-Vosko GGA (EVGGA) to indulgence the exchange correlation potential by solving Kohn–Sham equations. The result shows that the compound is metallic with sturdy hybridization near the Fermi energy level (E F ). The density of states at Fermi energy, N(E F ), is determined by the overlaping between B-p, B-s and Be-s states. This overlaping is strong enough indicating metallic origin with different values of N(E F ). These values are 16.4, 16.27 and 14.89 states/eV, and the corresponding bare linear low-temperature electronic specific heat coefficient (γ) is found to be 2.84, 2.82 and 2.58 mJ/mol K 2 for EVGGA, GGA and LDA respectively. There exists a strong hybridization between B-s and B-p states, also between B-s and Be-p states around the Fermi level. The Fermi surface is composed of three sheets. These sheets consist of set of holes and electrons. The bonding features of the compounds are analyzed using the electronic charge density in the (101 and −101) crystallographic planes and also the analyzing of charge density shows covalent bonding between B and B. The linear optical properties are also deliberated and discussed in particulars. - Highlights: • The compound is metallic. • The density of states at the Fermi energy is calculated. • The bare linear low-temperature electronic specific heat coefficient is obtained. • Fermi surface is composed of three sheets. • The bonding features are analyzed using the electronic charge density

  9. The outlook of innovative optical-electronic technologies implementation in transportation

    Science.gov (United States)

    Shilina, Elena V.; Ryabichenko, Roman B.

    2005-06-01

    Information and telecommunication technologies (ITT) are already tool economic development of society and their role will grow. The first task is providing of information security of ITT that is necessary for it distribution in "information" society. The state policy of the leading world countries (USA, France, Japan, Great Britain and China) is focused on investment huge funds in innovative technologies development. Within the next 4-6 years the main fiber-optic transfer lines will have data transfer speed 40 Gbit/s, number of packed channels 60-200 that will provide effective data transfer speed 2,4-8 Tbit/s. Photonic-crystalline fibers will be promising base of new generation fiber-optic transfer lines. The market of information imaging devices and digital photo cameras will be grown in 3-5 times. Powerful lasers based on CO2 and Nd:YAG will be actively used in transport machinery construction when producing aluminum constructions of light rolling-stock. Light-emitting diodes (LEDs) will be base for energy saving and safety light sources used for vehicles and indoor lighting. For example, in the USA cost reducing for lighting will be 200 billion dollars. Implementation analysis of optic electronic photonic technologies (OPT) in ground and aerospace systems shows that they provide significant increasing of traffic safety, crew and passengers comfort with help of smart vehicles construction and non-contact dynamic monitoring both transport facilities (for example, wheel flanges) and condition of rail track (road surface), equipping vehicles with night vision equipment. Scientific-technical programs of JSC "RZD" propose application of OPT in new generation systems: axle-box units for coaches and freight cars monitoring when they are moved, track condition analysis, mechanical stress and permanent way irregularity detection, monitoring geometric parameters of aerial contact wire, car truck, rail and wheel pair roll surface, light signals automatic detection from

  10. FINAL REPORT: Scalable Methods for Electronic Excitations and Optical Responses of Nanostructures: Mathematics to Algorithms to Observables

    Energy Technology Data Exchange (ETDEWEB)

    Chelikowsky, James R. [Univ. of Texas, Austin, TX (United States)

    2013-04-01

    Work in nanoscience has increased substantially in recent years owing to its potential technological applications and to fundamental scientific interest. A driving force for this activity is to capitalize on new phenomena that occurs at the nanoscale. For example, the physical confinement of electronic states, i.e., quantum confinement, can dramatically alter the electronic and optical properties of matter. A prime example of this occurs for the optical properties of nanoscale crystals such as those composed of elemental silicon. Silicon in the bulk state is optically inactive due to the small size of the optical gap, which can only be accessed by indirect transitions. However, at the nanoscale, this material becomes optically active. The size of the optical gap is increased by confinement and the conservation of crystal momentum ceases to hold, resulting in the viability of indirect transitions. Our work associated with this grant has focused on developing new scalable algorithms for describing the electronic and optical properties of matter at the nanoscale such as nano structures of silicon and related semiconductor properties.

  11. Electronic and optical properties of defect CdIn_2Te_4 chalcopyrite semiconductor: A first principle approach

    International Nuclear Information System (INIS)

    Mishra, S.; Ganguli, B.

    2016-01-01

    We present detailed study of structural, electronic and optical properties of CdIn_2Te_4 compound. The calculations are carried out using Density Functional theory based Tight Binding Linear Muffin Tin Orbital method. The compound is found to be direct band gap semiconductor with a band gap of 1.03 eV. The band gap is within the limit of LDA underestimation. The calculated structural parameters agree well with the available experimental values. We find a decrements of 9.6% in band gap and significant effects on overall electronic and optical properties due to structural distortions. These effects on optical properties come mainly from the change in transition probability. An-isotropic nature of optical properties get enhanced due to structural distortion. The Calculated real & imaginary parts of dielectric constant and static dielectric constant agree well with the available experimental result. - Highlights: • We present ab-initio calculations of electronic & optical properties of CdIn_2Te_4. • Band gap get reduced by 9.6% due to structural distortion. • Structural distortion has significant effects on optical properties. • Anisotropic nature of optical response functions get enhanced by structural distortion. • Calculated dielectric constant agrees with experimental value.

  12. The Influence of Negative Surprise on Hedonic Adaptation

    Directory of Open Access Journals (Sweden)

    Ana Paula Kieling

    2016-01-01

    Full Text Available After some time using a product or service, the consumer tends to feel less pleasure with consumption. This reduction of pleasure is known as hedonic adaptation. One of the emotions that interfere in this process is surprise. Based on two experiments, we suggest that negative surprise – differently to positive – influences with the level of pleasure foreseen and experienced by the consumer. Study 1 analyzes the influence of negative (vs. positive surprise on the consumer’s post-purchase hedonic adaptation expectation. Results showed that negative surprise influences the intensity of adaptation, augmenting its strength. Study 2 verifies the influence of negative (vs positive surprise over hedonic adaptation. The findings suggested that negative surprise makes adaptation happen more intensively and faster as time goes by, which brings consequences to companies and consumers in the post-purchase process, such as satisfaction and loyalty.

  13. Intraperitoneal Glucose Sensing is Sometimes Surprisingly Rapid

    Directory of Open Access Journals (Sweden)

    Anders Lyngvi Fougner

    2016-04-01

    Full Text Available Rapid, accurate and robust glucose measurements are needed to make a safe artificial pancreas for the treatment of diabetes mellitus type 1 and 2. The present gold standard of continuous glucose sensing, subcutaneous (SC glucose sensing, has been claimed to have slow response and poor robustness towards local tissue changes such as mechanical pressure, temperature changes, etc. The present study aimed at quantifying glucose dynamics from central circulation to intraperitoneal (IP sensor sites, as an alternative to the SC location. Intraarterial (IA and IP sensors were tested in three anaesthetized non-diabetic pigs during experiments with intravenous infusion of glucose boluses, enforcing rapid glucose level excursions in the range 70--360 mg/dL (approximately 3.8--20 mmol/L. Optical interferometric sensors were used for IA and IP measurements. A first-order dynamic model with time delay was fitted to the data after compensating for sensor dynamics. Additionally, off-the-shelf Medtronic Enlite sensors were used for illustration of SC glucose sensing. The time delay in glucose excursions from central circulation (IA to IP sensor location was found to be in the range 0--26 s (median: 8.5 s, mean: 9.7 s, SD 9.5 s, and the time constant was found to be 0.5--10.2 min (median: 4.8 min, mean: 4.7 min, SD 2.9 min. IP glucose sensing sites have a substantially faster and more distinctive response than SC sites when sensor dynamics is ignored, and the peritoneal fluid reacts even faster to changes in intravascular glucose levels than reported in previous animal studies. This study may provide a benchmark for future, rapid IP glucose sensors.

  14. A Dichotomic Analysis of the Surprise Examination Paradox

    OpenAIRE

    Franceschi, Paul

    2002-01-01

    This paper presents a dichotomic analysis of the surprise examination paradox. In section 1, I analyse the surprise notion in detail. I introduce then in section 2, the distinction between a monist and dichotomic analysis of the paradox. I also present there a dichotomy leading to distinguish two basically and structurally different versions of the paradox, respectively based on a conjoint and a disjoint definition of the surprise. In section 3, I describe the solution to SEP corresponding to...

  15. Damping effect of the inner band electrons on the optical absorption and bandwidth of metal nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ochoo, Lawrence, E-mail: lawijapuonj@yahoo.com; Migwi, Charles; Okumu, John [Kenyatta University, Physics Department (Kenya)

    2012-12-15

    Conflicts and discrepancies around nanoparticle (NP) size effect on the optical properties of metal NPs of sizes below the mean free path of electron can be traced to the internal damping effect of the hybrid resonance of the inner band (IB) and the conduction band (CB) electrons of the noble metals. We present a scheme to show how alternative mathematical formulation of the physics of interaction between the CB and the IB electrons of NP sizes <50 nm justifies this and resolves the conflicts. While a number of controversies exist between classical and quantum theories over the phenomenological factors to attribute to the NP size effect on the absorption bandwidth, this article shows that the bandwidth behavior can be well predicted from a different treatment of the IB damping effect, without invoking any of the controversial phenomenological factors. It finds that the IB damping effect is mainly frequency dependent and only partly size dependent and shows how its influence on the surface plasmon resonance can be modeled to show the influence of NP size on the absorption properties. Through the model, it is revealed that strong coupling of IB and CB electrons drastically alters the absorption spectra, splitting it into distinctive dipole and quadrupole modes and even introduce a behavioral switch. It finds a strong overlap between the IB and the CB absorptions for Au and Cu but not Ag, which is sensitive to the NP environment. The CB modes shift with the changing refractive index of the medium in a way that can allow their independent excitation, free of influence of the IB electrons. Through a hybrid of parameters, the model further finds that metal NP sizes can be established not only by their spectral absorption peak locations but also from a proper correlation of the peak location and the bandwidth (FWHM).

  16. Characterization and testing of 30 kV, 60 kW electron optical column for melting applications

    Energy Technology Data Exchange (ETDEWEB)

    Baibhaw, Prakash; Gupta, Sachin; Malik, Pravanjan, E-mail: bprakash@barc.gov.in [Bhabha Atomic Research Centre, Mumbai (India)

    2014-07-01

    High energy electron beams (30-150 keV) are widely used as intense heat source in welding, melting and evaporation of refractory metals. These operations are mostly carried out in high vacuum (10{sup -4}-10{sup -5} mbar) to aid unimpeded flow of electrons from generation to the point of application. A 30 kV, 60 kW Electron beam optical column (EOC) is designed and developed under the high power beam technology programme. The optical column consists of an electron gun and twin electromagnetic focusing lenses. The heating power of emitter, gun perveance, grid voltage control, beam focusing with the twin electromagnetic lenses and beam spot size measurements are reported in this paper. The results are compared with the design values. Operational issues during the high power melting and the strategy for automation of the electron gun are discussed. (author)

  17. Commissioning of an electro-optic electron bunch length monitor at FLASH

    International Nuclear Information System (INIS)

    Breunlin, Jonas

    2011-03-01

    The demands on the electron beam qualities for free-electron lasers (FEL) are challenging in terms of high peak currents. At FLASH, the high-gain FEL in Hamburg, longitudinal bunch compression is performed to achieve the requested high charge densities in short bunches. The precise control of the bunch compression process requires advanced diagnostics on the longitudinal bunch profile. The bunch length monitor presented in this thesis is based on a non-destructive detection using the electro-optic effect. The focus is on a compact and reliable system for permanent bunch diagnostics. The monitor provides single-shot measurements of the longitudinal bunch profiles with lengths of a few picoseconds by spectrally encoding their charge distribution. First measurements for characterization purpose have been performed. It has been shown that the monitor is suitable for monitoring the longitudinal bunch profile behind the first bunch compressor at FLASH. Electron bunch profiles with slopes corresponding to a full width half maximum of about 1.4 ps have been detected. That is the intrinsic resolution limit of the utilized method. (orig.)

  18. Optical Coating Performance and Thermal Structure Design for Heat Reflectors of JWST Electronic Control Unit

    Science.gov (United States)

    Quijada, Manuel A.; Threat, Felix; Garrison, Matt; Perrygo, Chuck; Bousquet, Robert; Rashford, Robert

    2008-01-01

    The James Webb Space Telescope (JWST) consists of an infrared-optimized Optical Telescope Element (OTE) that is cooled down to 40 degrees Kelvin. A second adjacent component to the OTE is the Integrated Science Instrument Module, or ISIM. This module includes the electronic compartment, which provides the mounting surfaces and ambient thermally controlled environment for the instrument control electronics. Dissipating the 200 watts generated from the ISIM structure away from the OTE is of paramount importance so that the spacecraft's own heat does not interfere with the infrared light detected from distant cosmic sources. This technical challenge is overcome by a thermal subsystem unit that provides passive cooling to the ISIM control electronics. The proposed design of this thermal radiator consists of a lightweight structure made out of composite materials and low-emittance metal coatings. In this paper, we will present characterizations of the coating emittance, bidirectional reflectance, and mechanical structure design that will affect the performance of this passive cooling system.

  19. Structural, Optical, and Electronic Characterization of Fe-Doped Alumina Nanoparticles

    Science.gov (United States)

    Heiba, Zein K.; Mohamed, Mohamed Bakr; Wahba, Adel Maher; Imam, N. G.

    2018-01-01

    The effects of iron doping on the structural, optical, and electronic properties of doped alumina have been studied. Single-phase iron-doped alumina Al2- x Fe x O3 ( x = 0.00 to 0.30) nanoparticles were synthesized via citrate-precursor method. Formation of single-phase hexagonal corundum structure with no other separate phases was demonstrated by x-ray diffraction (XRD) analysis and Fourier-transform infrared spectroscopy. The effects of iron doping on the α-Al2O3 structural parameters, viz. atomic coordinates, lattice parameters, crystallite size, and microstrain, were estimated from XRD data by applying the Rietveld profile fitting method. Transmission electron microscopy further confirmed the nanosize nature of the prepared samples with size ranging from 12 nm to 83 nm. The electronic band structure was investigated using density functional theory calculations to explain the decrease in the energy gap of Al2- x Fe x O3 as the amount of Fe was increased. The colored emission peaks in the visible region (blue, red, violet) of the electromagnetic spectrum obtained for the Fe-doped α-Al2O3 nanoparticles suggest their potential application as ceramic nanopigments.

  20. Optical signal response pf the alanine gel solution for photons and electrons clinical beams

    International Nuclear Information System (INIS)

    Silva, Cleber Feijo; Campos, Leticia Lucente

    2009-01-01

    Alanine gel dosimeter is a new gel material developed at IPEN that presents significant improvement on previous alanine systems developed by Costa (1994). The measure technique is based on the transformation of ferrous ions (Fe 2+ ) in ferric ions (Fe 3+ ) after irradiation. The DL-Alanine (C 3 H 7 NO 2 ) is an aminoacid tissue equivalent that improves the production of ferric ions in the solution. This work aims to study the comparison of optical signal response of the alanine gel solution for photons and electrons clinical beams. It was observed that the calibration factor can be considered independent of quality of the radiation for photons and electrons clinical beams. Therefore, it can be used the same calibration factor for evaluating the absorbed dose in photons and electrons fields in the energy of 6 MeV. Alanine Gel Dosimeter presents good performance and can be useful as alternative dosimeter in the radiotherapy area using MRI technique for 3D dose distribution evaluation. (author)

  1. Distributed grating-assisted coupler for optical all-dielectric electron accelerator

    Directory of Open Access Journals (Sweden)

    Zhiyu Zhang

    2005-07-01

    Full Text Available A Bragg waveguide consisting of multiple dielectric layers with alternating index of refraction becomes an excellent option to form electron accelerating structure powered by high power laser sources. It provides confinement of a synchronous speed-of-light mode with extremely low loss. However, laser field cannot be coupled into the structure collinearly with the electron beam. There are three requirements in designing input coupler for a Bragg electron accelerator: side coupling, selective mode excitation, and high coupling efficiency. We present a side-coupling scheme using a distributed grating-assisted coupler to inject the laser power into the waveguide. Side coupling is achieved by a grating with a period on the order of an optical wavelength. The phase matching condition results in resonance coupling thus providing selective mode excitation capability. The coupling efficiency is limited by profile matching between the outgoing beam and the incoming beam, which has normally a Gaussian profile. We demonstrate a nonuniform distributed grating structure generating an outgoing beam with a Gaussian profile, therefore, increasing the coupling efficiency.

  2. Electron beam and optical depth profiling of quasibulk GaN

    International Nuclear Information System (INIS)

    Chernyak, L.; Osinsky, A.; Nootz, G.; Schulte, A.; Jasinski, J.; Benamara, M.; Liliental-Weber, Z.; Look, D. C.; Molnar, R. J.

    2000-01-01

    Electron beam and optical depth profiling of thick (5.5--64 μm) quasibulk n-type GaN samples, grown by hydride vapor-phase epitaxy, were carried out using electron beam induced current (EBIC), microphotoluminescence (PL), and transmission electron microscopy (TEM). The minority carrier diffusion length, L, was found to increase linearly from 0.25 μm, at a distance of about 5 μm from the GaN/sapphire interface, to 0.63 μm at the GaN surface, for a 36-μm-thick sample. The increase in L was accompanied by a corresponding increase in PL band-to-band radiative transition intensity as a function of distance from the GaN/sapphire interface. We attribute the latter changes in PL intensity and minority carrier diffusion length to a reduced carrier mobility and lifetime at the interface, due to scattering at threading dislocations. The results of EBIC and PL measurements are in good agreement with the values for dislocation density obtained using TEM

  3. Ultrafast optical snapshots of hybrid perovskites reveal the origin of multiband electronic transitions

    Science.gov (United States)

    Appavoo, Kannatassen; Nie, Wanyi; Blancon, Jean-Christophe; Even, Jacky; Mohite, Aditya D.; Sfeir, Matthew Y.

    2017-11-01

    Connecting the complex electronic excitations of hybrid perovskites to their intricate organic-inorganic lattice structure has critical implications for energy conversion and optoelectronic technologies. Here we detail the multiband, multivalley electronic structure of a halide hybrid perovskite by measuring the absorption transients of a millimeter-scale-grain thin film as it undergoes a thermally controlled reversible tetragonal-to-orthogonal phase transition. Probing nearly single grains of this hybrid perovskite, we observe an unreported energy splitting (degeneracy lifting) of the high-energy 2.6 eV band in the tetragonal phase that further splits as the rotational degrees of freedom of the disordered C H3N H3 + molecules are reduced when the sample is cooled. This energy splitting drastically increases during an extended phase-transition coexistence region that persists from 160 to 120 K, becoming more pronounced in the orthorhombic phase. By tracking the temperature-dependent optical transition energies and using symmetry analysis that describes the evolution of electronic states from the tetragonal phase to the orthorhombic phase, we assign this energy splitting to the nearly degenerate transitions in the tetragonal phase from both the R - and M -point-derived states. Importantly, these assignments explain how momentum conservation effects lead to long hot-carrier lifetimes in the room-temperature tetragonal phase, with faster hot-carrier relaxation when the hybrid perovskite structurally transitions to the orthorhombic phase due to enhanced scattering at the Γ point.

  4. RESEARCH ON THE ELECTRONIC AND OPTICAL PROPERTIES OF POLYMER AND OTHER ORGANIC MOLECULAR THIN FILMS

    Energy Technology Data Exchange (ETDEWEB)

    ALEXEI G. VITUKHNOVSKY; IGOR I. SOBELMAN - RUSSIAN ACADEMY OF SCIENCES

    1995-09-06

    Optical properties of highly ordered films of poly(p-phenylene) (PPP) on different substrates, thin films of mixtures of conjugated polymers, of fullerene and its composition with polymers, molecular J-aggregates of cyanine dyes in frozen matrices have been studied within the framework of the Agreement. Procedures of preparation of high-quality vacuum deposited PPP films on different substrates (ITO, Si, GaAs and etc.) were developed. Using time-correlated single photon counting technique and fluorescence spectroscopy the high quality of PPP films has been confirmed. Dependence of structure and optical properties on the conditions of preparation were investigated. The fluorescence lifetime and spectra of highly oriented vacuum deposited PPP films were studied as a function of the degree of polymerization. It was shown for the first time that the maximum fluorescence quantum yield is achieved for the chain length approximately equal to 35 monomer units. The selective excitation of luminescence of thin films of PPP was performed in the temperature range from 5 to 300 K. The total intensity of luminescence monotonically decreases with decreasing temperature. Conditions of preparation of highly cristallyne fullerene C{sub 60} films by the method of vacuum deposition were found. Composites of C{sub 60} with conjugated polymers PPV and polyacetylene (PA) were prepared. The results on fluorescence quenching, IR and resonant Raman spectroscopy are consistent with earlier reported ultrafast photoinduced electron transfer from PPV to C{sub 60} and show that the electron transfer is absent in the case of the PA-C{sub 60} composition. Strong quenching of PPV fluorescence was observed in the PPV-PA blends. The electron transfer from PPV to PA can be considered as one of the possible mechanisms of this quenching. The dynamics of photoexcitations in different types of J-aggregates of the carbocyanine dye was studied at different temperatures in frozen matrices. The optical

  5. Universal quantum gates on electron-spin qubits with quantum dots inside single-side optical microcavities.

    Science.gov (United States)

    Wei, Hai-Rui; Deng, Fu-Guo

    2014-01-13

    We present some compact quantum circuits for a deterministic quantum computing on electron-spin qubits assisted by quantum dots inside single-side optical microcavities, including the CNOT, Toffoli, and Fredkin gates. They are constructed by exploiting the giant optical Faraday rotation induced by a single-electron spin in a quantum dot inside a single-side optical microcavity as a result of cavity quantum electrodynamics. Our universal quantum gates have some advantages. First, all the gates are accomplished with a success probability of 100% in principle. Second, our schemes require no additional electron-spin qubits and they are achieved by some input-output processes of a single photon. Third, our circuits for these gates are simple and economic. Moreover, our devices for these gates work in both the weak coupling and the strong coupling regimes, and they are feasible in experiment.

  6. Interaction of low-energy electrons and positrons with condensed matter: Stopping powers and inelastic mean free paths from optical data

    International Nuclear Information System (INIS)

    Ashley, J.C.

    1989-01-01

    An ''optical-data model'' is described for evaluating energy loss per unit pathlength and inelastic mean free path for low-energy electrons and positrons (approx lt 10 keV) from optical data on the medium of interest. Exchange between the incident electron and electrons in the medium is included. Results from the optical-data model are compared with previous theoretical calculations. 15 refs., 6 figs., 2 tabs

  7. Optically controlled seeding of Raman forward scattering and injection of electrons in a self-modulated laser-wakefield accelerator

    International Nuclear Information System (INIS)

    Chen, W.-T.; Chien, T.-Y.; Lee, C.-H.; Lin, J.-Y.; Wang, J.; Chen, S.-Y.

    2004-01-01

    Optical seeding of plasma waves and the injection of electrons are key issues in self-modulated laser-wakefield accelerators. By implementing a copropagating laser prepulse with proper timing, we are able to control the growth of Raman forward scattering and the production of accelerated electrons. The dependence of the Raman intensity on prepulse timing indicates that the seeding of Raman forward scattering is dominated by the ionization-induced wakefield, and the dependence of the divergence and number of accelerated electrons further reveals that the stimulated Raman backward scattering of the prepulse plays the essential role of injecting hot electrons into the fast plasma wave driven by the main pulse

  8. Optical Coating Performance for Heat Reflectors of the JWST-ISIM Electronic Component

    Science.gov (United States)

    Rashford, Robert A.; Perrygo, Charles M.; Garrison, Matthew B.; White, Bryant K.; Threat, Felix T.; Quijada, Manuel A.; Jeans, James W.; Huber, Frank K.; Bousquet, Robert R.; Shaw, Dave

    2011-01-01

    A document discusses a thermal radiator design consisting of lightweight composite materials and low-emittance metal coatings for use on the James Webb Space Telescope (JWST) structure. The structure will have a Thermal Subsystem unit to provide passive cooling to the Integrated Science Instrument Module (ISIM) control electronics. The ISIM, in the JWST observatory, is the platform that provides the mounting surfaces for the instrument control electronics. Dissipating the control electronic generated-heat away from JWST is of paramount importance so that the spacecraft s own heat does not interfere with the infrared-light gathering of distant cosmic sources. The need to have lateral control in the emission direction of the IEC (ISIM Electronics Compartment) radiators led to the development of a directional baffle design that uses multiple curved mirrorlike surfaces. This concept started out from the so-called Winston non-imaging optical concentrators that use opposing parabolic reflector surfaces, where each parabola has its focus at the opposite edge of the exit aperture. For this reason they are often known as compound parabolic concentrators or CPCs. This radiator system with the circular section was chosen for the IEC reflectors because it offers two advantages over other designs. The first is that the area of the reflector strips for a given radiator area is less, which results in a lower mass baffle assembly. Secondly, the fraction of energy emitted by the radiator strips and subsequently reflected by the baffle is less. These fewer reflections reduced the amount of energy that is absorbed and eventually re-emitted, typically in a direction outside the design emission range angle. A baffle frame holds the mirrors in position above a radiator panel on the IEC. Together, these will direct the majority of the heat from the IEC above the sunshield away towards empty space.

  9. Ab initio calculations of indium arsenide in the wurtzite phase: structural, electronic and optical properties

    International Nuclear Information System (INIS)

    Dacal, Luis C O; Cantarero, A

    2014-01-01

    Most III–V semiconductors, which acquire the zinc-blende phase as bulk materials, adopt the metastable wurtzite phase when grown in the form of nanowires. These are new semiconductors with new optical properties, in particular, a different electronic band gap when compared with that grown in the zinc-blende phase. The electronic gap of wurtzite InAs at the Γ–point of the Brillouin zone (E 0 gap) has been recently measured, E 0 =0.46 eV at low temperature. The electronic gap at the A–point of the Brillouin zone (equivalent to the L–point in the zinc-blende structure, E 1 ) has also been obtained recently based on a resonant Raman scattering experiment. In this work, we calculate the band structure of InAs in the zinc-blende and wurtzite phases, using the full potential linearized augmented plane wave method, including spin-orbit interaction. The electronic band gap has been improved through the modified Becke–Johnson exchange-correlation potential. Both the E 0 and E 1 gaps agree very well with the experiment. From the calculations, a crystal field splitting of 0.122 eV and a spin-orbit splitting of 0.312 eV (the experimental value in zinc-blende InAs is 0.4 eV) has been obtained. Finally, we calculate the dielectric function of InAs in both the zinc-blende and wurtzite phases and a comparative discussion is given. (paper)

  10. Ab initio calculations of indium arsenide in the wurtzite phase: structural, electronic and optical properties

    Science.gov (United States)

    Dacal, Luis C. O.; Cantarero, A.

    2014-03-01

    Most III-V semiconductors, which acquire the zinc-blende phase as bulk materials, adopt the metastable wurtzite phase when grown in the form of nanowires. These are new semiconductors with new optical properties, in particular, a different electronic band gap when compared with that grown in the zinc-blende phase. The electronic gap of wurtzite InAs at the \\Gamma -point of the Brillouin zone ({{E}_{0}} gap) has been recently measured, {{E}_{0}}=0.46 eV at low temperature. The electronic gap at the A-point of the Brillouin zone (equivalent to the L-point in the zinc-blende structure, {{E}_{1}}) has also been obtained recently based on a resonant Raman scattering experiment. In this work, we calculate the band structure of InAs in the zinc-blende and wurtzite phases, using the full potential linearized augmented plane wave method, including spin-orbit interaction. The electronic band gap has been improved through the modified Becke-Johnson exchange-correlation potential. Both the {{E}_{0}} and {{E}_{1}} gaps agree very well with the experiment. From the calculations, a crystal field splitting of 0.122 eV and a spin-orbit splitting of 0.312 eV (the experimental value in zinc-blende InAs is 0.4 eV) has been obtained. Finally, we calculate the dielectric function of InAs in both the zinc-blende and wurtzite phases and a comparative discussion is given.

  11. Optically controlled laser-plasma electron accelerator for compact gamma-ray sources

    Science.gov (United States)

    Kalmykov, S. Y.; Davoine, X.; Ghebregziabher, I.; Shadwick, B. A.

    2018-02-01

    Generating quasi-monochromatic, femtosecond γ-ray pulses via Thomson scattering (TS) demands exceptional electron beam (e-beam) quality, such as percent-scale energy spread and five-dimensional brightness over 1016 A m-2. We show that near-GeV e-beams with these metrics can be accelerated in a cavity of electron density, driven with an incoherent stack of Joule-scale laser pulses through a mm-size, dense plasma (n 0 ˜ 1019 cm-3). Changing the time delay, frequency difference, and energy ratio of the stack components controls the e-beam phase space on the femtosecond scale, while the modest energy of the optical driver helps afford kHz-scale repetition rate at manageable average power. Blue-shifting one stack component by a considerable fraction of the carrier frequency makes the stack immune to self-compression. This, in turn, minimizes uncontrolled variation in the cavity shape, suppressing continuous injection of ambient plasma electrons, preserving a single, ultra-bright electron bunch. In addition, weak focusing of the trailing component of the stack induces periodic injection, generating, in a single shot, a train of bunches with controllable energy spacing and femtosecond synchronization. These designer e-beams, inaccessible to conventional acceleration methods, generate, via TS, gigawatt γ-ray pulses (or multi-color pulse trains) with the mean energy in the range of interest for nuclear photonics (4-16 MeV), containing over 106 photons within a microsteradian-scale observation cone.

  12. Band resolution of optical spectra of solvated electrons in water, alcohols, and tetrahydrofuran

    International Nuclear Information System (INIS)

    Jou, F.-Y.; Freeman, G.R.

    1979-01-01

    The optical absorption spectra of solvated electrons in water, alcohols, and tetrahydrofuran are empirically resolved into two Gaussian bands and a continuum tail. The first Gaussian band covers most of the low energy side of the spectrum. The second Gaussian band lies at an energy slightly above that of the absorption maximum of the total spectrum. With the exception of tert-butyl alcohol, in water and alcohols the following were observed: (a) the first Gaussian bands have the same half-width, but the oscillator strength in water is about double that in an alcohol; (b) the second Gaussian bands have similar half-widths and oscillator strengths; (c) the continuum tails have similar half-widths, yet that in water possesses only about one third as much oscillator strength as the one in alcohol. In tert-butyl alcohol and tetrahydrofuran the first Gaussian band and the continuum tail each carry nearly half of the total oscillator strength. (author)

  13. Comparison endpoint study of process plasma and secondary electron beam exciter optical emission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Stephan Thamban, P. L.; Yun, Stuart; Padron-Wells, Gabriel; Hosch, Jimmy W.; Goeckner, Matthew J. [Department of Mechanical Engineering, University of Texas at Dallas, 800W Campbell Road, Richardson, Texas 75080 (United States); Department of Electrical Engineering, University of Texas at Dallas, 800W Campbell Road, Richardson, Texas 75080 (United States); Verity Instruments, Inc., 2901 Eisenhower Street, Carrollton, Texas 75007 (United States); Department of Mathematical Sciences, University of Texas at Dallas, 800 W Campbell Road, Richardson, Texas 75080 (United States)

    2012-11-15

    Traditionally process plasmas are often studied and monitored by optical emission spectroscopy. Here, the authors compare experimental measurements from a secondary electron beam excitation and direct process plasma excitation to discuss and illustrate its distinctiveness in the study of process plasmas. They present results that show excitations of etch process effluents in a SF{sub 6} discharge and endpoint detection capabilities in dark plasma process conditions. In SF{sub 6} discharges, a band around 300 nm, not visible in process emission, is observed and it can serve as a good indicator of etch product emission during polysilicon etches. Based on prior work reported in literature the authors believe this band is due to SiF{sub 4} gas phase species.

  14. Chaos in Dirac Electron Optics: Emergence of a Relativistic Quantum Chimera.

    Science.gov (United States)

    Xu, Hong-Ya; Wang, Guang-Lei; Huang, Liang; Lai, Ying-Cheng

    2018-03-23

    We uncover a remarkable quantum scattering phenomenon in two-dimensional Dirac material systems where the manifestations of both classically integrable and chaotic dynamics emerge simultaneously and are electrically controllable. The distinct relativistic quantum fingerprints associated with different electron spin states are due to a physical mechanism analogous to a chiroptical effect in the presence of degeneracy breaking. The phenomenon mimics a chimera state in classical complex dynamical systems but here in a relativistic quantum setting-henceforth the term "Dirac quantum chimera," associated with which are physical phenomena with potentially significant applications such as enhancement of spin polarization, unusual coexisting quasibound states for distinct spin configurations, and spin selective caustics. Experimental observations of these phenomena are possible through, e.g., optical realizations of ballistic Dirac fermion systems.

  15. Chaos in Dirac Electron Optics: Emergence of a Relativistic Quantum Chimera

    Science.gov (United States)

    Xu, Hong-Ya; Wang, Guang-Lei; Huang, Liang; Lai, Ying-Cheng

    2018-03-01

    We uncover a remarkable quantum scattering phenomenon in two-dimensional Dirac material systems where the manifestations of both classically integrable and chaotic dynamics emerge simultaneously and are electrically controllable. The distinct relativistic quantum fingerprints associated with different electron spin states are due to a physical mechanism analogous to a chiroptical effect in the presence of degeneracy breaking. The phenomenon mimics a chimera state in classical complex dynamical systems but here in a relativistic quantum setting—henceforth the term "Dirac quantum chimera," associated with which are physical phenomena with potentially significant applications such as enhancement of spin polarization, unusual coexisting quasibound states for distinct spin configurations, and spin selective caustics. Experimental observations of these phenomena are possible through, e.g., optical realizations of ballistic Dirac fermion systems.

  16. Electron optics design of an 8-in. spherical MCP-PMT

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Ping, E-mail: chenping@opt.cn [Key Laboratory of Ultra-fast photoelectric Diagnostics Technology, Xi’an Institute of Optics and Precision Mechanics (XIOPM), Chinese Academy of Sciences, Xi’an 710119 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, Shanxi (China); Tian, Jinshou [Key Laboratory of Ultra-fast photoelectric Diagnostics Technology, Xi’an Institute of Optics and Precision Mechanics (XIOPM), Chinese Academy of Sciences, Xi’an 710119 (China); Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, Shanxi (China); Qian, Sen; Zhao, Tianchi [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Liu, Hulin; Wei, Yonglin; Sai, Xiaofeng; He, Jianping; Wang, Xing; Lu, Yu [Key Laboratory of Ultra-fast photoelectric Diagnostics Technology, Xi’an Institute of Optics and Precision Mechanics (XIOPM), Chinese Academy of Sciences, Xi’an 710119 (China); Chen, Lin; Guo, Lehui; Pei, Chengquan; Hui, Dandan [Key Laboratory of Ultra-fast photoelectric Diagnostics Technology, Xi’an Institute of Optics and Precision Mechanics (XIOPM), Chinese Academy of Sciences, Xi’an 710119 (China); University of Chinese Academy of Sciences, Beijing 100049 (China)

    2017-03-11

    This paper discusses the electron optical system of an 8-in. spherical MCP-PMT. The MCP assembly, the supporting pole and the supply voltages are carefully designed to optimize the photoelectron collection efficiency and the transit time spread. Coating the MCP nickel-chromium electrode with an additional high secondary emission material is employed to make a breakthrough on the collection efficiency. With the simulation software CST, the Finite Integration method and the Monte Carlo method are combined to evaluate the collection efficiency, the time properties and the Earth's magnetic field effects. Simulation results show that the photocathode active solid angle is over 3.5 πsr, the average collection efficiency can exceed 95% with the coated MCP and the mean transit time spread is 2.2 ns for a typical electric potential of 500 V applied between the photocathode and the MCP input facet. The prototype and the measured single photoelectron spectrum are also presented.

  17. Coma-free alignment of high resolution electron microscopes with the aid of optical diffractograms

    International Nuclear Information System (INIS)

    Zemlin, F.; Weiss, K.; Schiske, P.; Kunath, W.; Herrmann, K.-H.

    1978-01-01

    Alignment by means of current commutating and defocusing of the objective does not yield the desired rotational symmetry of the imaging pencils. This was found while aligning a transmission electron microscope with a single field condenser objective. A series of optical diffractograms of micrographs taken under the same tilted illumination yet under various azimuths have been arranged in a tableau, wherein strong asymmetry is exhibited. Quantitative evaluation yields the most important asymmetric aberration to be the axial coma, which becomes critical when a resolution better than 5 A 0 is obtained. The tableau also allows an assessment of the three-fold astigmatism. A procedure has been developed which aligns the microscope onto the coma-free and dispersion-free pencil axis and does not rely on current communication. The procedure demands equal appearance of astigmatic carbon film images produced under the same tilt yet diametrical azimuth. (Auth.)

  18. Optics of beam recirculation in the CEBAF [Continuous Electron Beam Accelerator Facility] cw linac

    International Nuclear Information System (INIS)

    Douglas, D.R.

    1986-01-01

    The use of recirculation in linear accelerator designs requires beam transport systems that will not degrade beam quality. We present a design for the transport lines to be used during recirculation in the CEBAF accelerator. These beam lines are designed to avoid beam degradation through synchrotron radiation excitation or betatron motion mismatch, are insensitive to errors commonly encountered during beam transport, and are optimized for electron beams with energies of 0.5 to 6.0 GeV. Optically, they are linearly isochronous second order achromats based on a ''missing magnet'' FODO structure. We give lattice specifications for, and results of analytic estimates and numerical simulations of the performance of, the beam transport system

  19. Determination of Electron Optical Properties for Aperture Zoom Lenses Using an Artificial Neural Network Method.

    Science.gov (United States)

    Isik, Nimet

    2016-04-01

    Multi-element electrostatic aperture lens systems are widely used to control electron or charged particle beams in many scientific instruments. By means of applied voltages, these lens systems can be operated for different purposes. In this context, numerous methods have been performed to calculate focal properties of these lenses. In this study, an artificial neural network (ANN) classification method is utilized to determine the focused/unfocused charged particle beam in the image point as a function of lens voltages for multi-element electrostatic aperture lenses. A data set for training and testing of ANN is taken from the SIMION 8.1 simulation program, which is a well known and proven accuracy program in charged particle optics. Mean squared error results of this study indicate that the ANN classification method provides notable performance characteristics for electrostatic aperture zoom lenses.

  20. An optical parametric chirped-pulse amplifier for seeding high repetition rate free-electron lasers

    International Nuclear Information System (INIS)

    Höppner, H; Hage, A; Tanikawa, T; Schulz, M; Faatz, B; Riedel, R; Prandolini, M J; Teubner, U; Tavella, F

    2015-01-01

    High repetition rate free-electron lasers (FEL), producing highly intense extreme ultraviolet and x-ray pulses, require new high power tunable femtosecond lasers for FEL seeding and FEL pump-probe experiments. A tunable, 112 W (burst mode) optical parametric chirped-pulse amplifier (OPCPA) is demonstrated with center frequencies ranging from 720–900 nm, pulse energies up to 1.12 mJ and a pulse duration of 30 fs at a repetition rate of 100 kHz. Since the power scalability of this OPCPA is limited by the OPCPA-pump amplifier, we also demonstrate a 6.7–13.7 kW (burst mode) thin-disk OPCPA-pump amplifier, increasing the possible OPCPA output power to many hundreds of watts. Furthermore, third and fourth harmonic generation experiments are performed and the results are used to simulate a seeded FEL with high-gain harmonic generation. (paper)

  1. Electronic and Optical Properties of Sodium Niobate: A Density Functional Theory Study

    Directory of Open Access Journals (Sweden)

    Daniel Fritsch

    2018-01-01

    Full Text Available In recent years, much effort has been devoted to replace the most commonly used piezoelectric ceramic lead zirconate titanate Pb[ZrxTi1−x]O3 (PZT with a suitable lead-free alternative for memory or piezoelectric applications. One possible alternative to PZT is sodium niobate as it exhibits electrical and mechanical properties that make it an interesting material for technological applications. The high-temperature simple cubic perovskite structure undergoes a series of structural phase transitions with decreasing temperature. However, particularly the phases at room temperature and below are not yet fully characterised and understood. Here, we perform density functional theory calculations for the possible phases at room temperature and below and report on the structural, electronic, and optical properties of the different phases in comparison to experimental findings.

  2. Small molecules make big differences: molecular doping effects on electronic and optical properties of phosphorene

    International Nuclear Information System (INIS)

    Jing, Yu; Tang, Qing; He, Peng; Zhou, Zhen; Shen, Panwen

    2015-01-01

    Systematical computations on the density functional theory were performed to investigate the adsorption of three typical organic molecules, tetracyanoquinodimethane (TCNQ), tetracyanoethylene (TCNE) and tetrathiafulvalene (TTF), on the surface of phosphorene monolayers and thicker layers. There exist considerable charge transfer and strong non-covalent interaction between these molecules and phosphorene. In particular, the band gap of phosphorene decreases dramatically due to the molecular modification and can be further tuned by applying an external electric field. Meanwhile, surface molecular modification has proven to be an effective way to enhance the light harvesting of phosphorene in different directions. Our results predict a flexible method toward modulating the electronic and optical properties of phosphorene and shed light on its experimental applications. (paper)

  3. Electronic structure and optical properties of boron nitride nanotube bundles from first principles

    Science.gov (United States)

    Behzad, Somayeh

    2015-06-01

    The electronic and optical properties of bundled armchair and zigzag boron nitride nanotubes (BNNTs) are investigated by using density functional theory. Owing to the inter-tube coupling, the dispersions along the tube axis and in the plane perpendicular to the tube axis of BNNT bundles are significantly varied, which are characterized by the decrease of band gap, the splitting of the doubly degenerated states, the expansions of valence and conduction bands. The calculated dielectric functions of the armchair and zigzag bundles are similar to that of the isolated tubes, except for the appearance of broadened peaks, small shifts of peak positions about 0.1 eV and increasing of peak intensities.

  4. Techniques for fabricating an infrared optical pyrometry system for pulsed electron beam diagnostics

    International Nuclear Information System (INIS)

    Ouellette, A.L.

    1976-01-01

    A description is given of an infrared optical pyrometry system which was designed to make fast time resolved temperature measurements. The purpose of this equipment is to determine the amount of energy from an electron beam or some other type of pulsed energy deposition that is absorbed in a target. The system is capable of measuring energy deposition levels up to 4000 J/g in carbon, which corresponds to a graphite target temperature of 2200 0 C. Methods of fabrication, alignment, and calibration are presented. The measurement of absorbed energy in a target as a function of position and depth is discussed as a possible application, and several measurements are described which permit a comparison of results from this system with those taken by other methods

  5. First principle electronic, structural, elastic, and optical properties of strontium titanate

    Directory of Open Access Journals (Sweden)

    Chinedu E. Ekuma

    2012-03-01

    Full Text Available We report self-consistent ab-initio electronic, structural, elastic, and optical properties of cubic SrTiO3 perovskite. Our non-relativistic calculations employed a generalized gradient approximation (GGA potential and the linear combination of atomic orbitals (LCAO formalism. The distinctive feature of our computations stem from solving self-consistently the system of equations describing the GGA, using the Bagayoko-Zhao-Williams (BZW method. Our results are in agreement with experimental ones where the later are available. In particular, our theoretical, indirect band gap of 3.24 eV, at the experimental lattice constant of 3.91 Å, is in excellent agreement with experiment. Our predicted, equilibrium lattice constant is 3.92 Å, with a corresponding indirect band gap of 3.21 eV and bulk modulus of 183 GPa.

  6. Optics

    CERN Document Server

    Mathieu, Jean Paul

    1975-01-01

    Optics, Parts 1 and 2 covers electromagnetic optics and quantum optics. The first part of the book examines the various of the important properties common to all electromagnetic radiation. This part also studies electromagnetic waves; electromagnetic optics of transparent isotropic and anisotropic media; diffraction; and two-wave and multi-wave interference. The polarization states of light, the velocity of light, and the special theory of relativity are also examined in this part. The second part is devoted to quantum optics, specifically discussing the classical molecular theory of optical p

  7. Summary of radiation-induced transient absorption and recovery in fiber optic waveguides. [Pulsed electrons and x-rays

    Energy Technology Data Exchange (ETDEWEB)

    Skoog, C.D.

    1976-11-01

    The absorption induced in fiber optic waveguides by pulsed electron and X-ray radiation has been measured as a function of optical wavelength from 450 to 950 nm, irradiation temperature from -54 to 71/sup 0/C, and dose from 1 to 500 krads. The fibers studied are Ge-doped silica core fibers (Corning Low Loss), ''pure'' vitreous silica core fibers (Schott, Bell Laboratories, Fiberoptic Cable Corp., and Valtec Fiberoptics), polymethyl-methacrylate core fibers (DuPont CROFON and PFX), and polystyrene core fibers (International Fiber Optics and Polyoptics). Models that have been developed to account for the observed absorption recovery are also summarized.

  8. The Value of Surprising Findings for Research on Marketing

    OpenAIRE

    JS Armstrong

    2004-01-01

    In the work of Armstrong (Journal of Business Research, 2002), I examined empirical research on the scientific process and related these to marketing science. The findings of some studies were surprising. In this reply, I address surprising findings and other issues raised by commentators.

  9. Doping in silicon nanocrystals: An ab initio study of the structural, electronic and optical properties

    International Nuclear Information System (INIS)

    Iori, Federico; Degoli, Elena; Luppi, Eleonora; Magri, Rita; Marri, Ivan; Cantele, G.; Ninno, D.; Trani, F.; Ossicini, Stefano

    2006-01-01

    There are experimental evidences that doping control at the nanoscale can significantly modify the optical properties with respect to the pure systems. This is the case of silicon nanocrystals (Si-nc), for which it has been shown that the photoluminescence (PL) peak can be tuned also below the bulk Si band gap by properly controlling the impurities, for example by boron (B) and phosphorus (P) codoping. In this work, we report on an ab initio study of impurity states in Si-nc. We consider B and P substitutional impurities for Si-nc with a diameter up to 2.2 nm. Formation energies (FEs), electronic, optical and structural properties have been determined as a function of the cluster dimension. For both B-doped and P-doped Si-nc the FE increases on decreasing the dimension, showing that the substitutional doping gets progressively more difficult for the smaller nanocrystals. Moreover, subsurface impurity positions result to be the most stable ones. The codoping reduces the FE strongly favoring this process with respect to the simple n-doping or p-doping. Such an effect can be attributed to charge compensation between the donor and the acceptor atoms. Moreover, smaller structural deformations, with respect to n-doped and p-doped cases, localized only around the impurity sites are observed. The band gap and the optical threshold are largely reduced with respect to the undoped Si-nc showing the possibility of an impurity-based engineering of the Si-nc PL properties

  10. Consumer electronic optics: how small can a lens be: the case of panomorph lenses

    Science.gov (United States)

    Thibault, Simon; Parent, Jocelyn; Zhang, Hu; Du, Xiaojun; Roulet, Patrice

    2014-09-01

    In 2014, miniature camera modules are applied to a variety of applications such as webcam, mobile phone, automotive, endoscope, tablets, portable computers and many other products. Mobile phone cameras are probably one of the most challenging parts due to the need for smaller and smaller total track length (TTL) and optimized embedded image processing algorithms. As the technology is developing, higher resolution and higher image quality, new capabilities are required to fulfil the market needs. Consequently, the lens system becomes more complex and requires more optical elements and/or new optical elements. What is the limit? How small an injection molded lens can be? We will discuss those questions by comparing two wide angle lenses for consumer electronic market. The first lens is a 6.56 mm (TTL) panoramic (180° FOV) lens built in 2012. The second is a more recent (2014) panoramic lens (180° FOV) with a TTL of 3.80 mm for mobile phone camera. Both optics are panomorph lenses used with megapixel sensors. Between 2012 and 2014, the development in design and plastic injection molding allowed a reduction of the TTL by more than 40%. This TTL reduction has been achieved by pushing the lens design to the extreme (edge/central air and material thicknesses as well as lens shape). This was also possible due to a better control of the injection molding process and material (low birefringence, haze and thermal stability). These aspects will be presented and discussed. During the next few years, we don't know if new material will come or new process but we will still need innovative people and industries to push again the limits.

  11. pH-Induced Surface Modification of Atomically Precise Silver Nanoclusters: An Approach for Tunable Optical and Electronic Properties

    KAUST Repository

    AbdulHalim, Lina G.

    2016-10-24

    Noble metal nanoclusters (NCs) play a pivotal role in bridging the gap between molecules and quantum dots. Fundamental understanding of the evolution of the structural, optical, and electronic properties of these materials in various environments is of paramount importance for many applications. Using state-of-the-art spectroscopy, we provide the first decisive experimental evidence that the structural, electronic, and optical properties of Ag-44(MNBA)(30) NCs can now be tailored by controlling the chemical environment. Infrared and photoelectron spectroscopies clearly indicate that there is a dimerization between two adjacent ligands capping the NCs that takes place upon lowering the pH from 13 to 7.

  12. Monochromaticity of optical radiation of Smith-Purcell generated by electron beam with 75 keV energy

    International Nuclear Information System (INIS)

    Adishchev, Yu.N.; Vukolov, A.V.; Karlovets, D.V.; Potylitsyn, A.P.; Kube, G.

    2005-01-01

    The monochromatism of the Smith-Purcell optical radiation generated by a 75-keV electron beam with a final emittance of ε = 0.65 x 10 -4 mm rad that passes over an optical grating with a period of D = 0.833 μm has been analyzed. It has been shown that the monochromatism (line width) of the Smith-Purcell radiation is determined not only by the angular aperture of a monochromator but also by the divergence of the electron beam [ru

  13. The effect of oxygen impurity on the electronic and optical properties of calcium, strontium and barium chalcogenide compounds

    International Nuclear Information System (INIS)

    Dadsetani, M.; Beiranvand, R.

    2010-01-01

    Electronic and optical properties of calcium, strontium and barium chalcogenide compounds in NaCl structure are studied using the band structure results obtained through the full potential linearized augmented palne wave method. Different linear relationships are observed between theoretical band gap and 1/a 2 (where a is lattice constant) for calcium, strontium and barium chalcogenide compounds with and without oxygen, respectively. An abnormal behavior of electronic and optical properties are found for compounds containing oxygen. These effects are ascribed to the special properties of Ca-O, Sr-O and Ba-O bonds, which are different from chemical bonds between Ca, Sr and Ba and other chalcogen atoms.

  14. Electron microscopy of primary cell cultures in solution and correlative optical microscopy using ASEM

    International Nuclear Information System (INIS)

    Hirano, Kazumi; Kinoshita, Takaaki; Uemura, Takeshi; Motohashi, Hozumi; Watanabe, Yohei; Ebihara, Tatsuhiko; Nishiyama, Hidetoshi; Sato, Mari; Suga, Mitsuo; Maruyama, Yuusuke; Tsuji, Noriko M.; Yamamoto, Masayuki; Nishihara, Shoko; Sato, Chikara

    2014-01-01

    Correlative light-electron microscopy of cells in a natural environment of aqueous liquid facilitates high-throughput observation of protein complex formation. ASEM allows the inverted SEM to observe the wet sample from below, while an optical microscope observes it from above quasi-simultaneously. The disposable ASEM dish with a silicon nitride (SiN) film window can be coated variously to realize the primary-culture of substrate-sensitive cells in a few milliliters of culture medium in a stable incubator environment. Neuron differentiation, neural networking, proplatelet-formation and phagocytosis were captured by optical or fluorescence microscopy, and imaged at high resolution by gold-labeled immuno-ASEM with/without metal staining. Fas expression on the cell surface was visualized, correlated to the spatial distribution of F-actin. Axonal partitioning was studied using primary-culture neurons, and presynaptic induction by GluRδ2-N-terminus-linked fluorescent magnetic beads was correlated to the presynaptic-marker Bassoon. Further, megakaryocytes secreting proplatelets were captured, and P-selectins with adherence activity were localized to some of the granules present by immuno-ASEM. The phagocytosis of lactic acid bacteria by dendritic cells was also imaged. Based on these studies, ASEM correlative microscopy promises to allow the study of various mesoscopic-scale dynamics in the near future. - Highlights: • In situ correlative light electron microscopy of samples in open solution by ASEM. • Primary cultures for in-solution CLEM by developing SiN-film coating methods • First visualization of fluorescent magnetic beads in aqueous solution by CLEM. • Presynaptic induction of neurons by GluRδ2-N-terminus-coated beads studied by CLEM. • Axonal partitioning, bacterial phagocytosis, platelet formation imaged by CLEM

  15. Single crystal growth, electronic structure and optical properties of Cs2HgBr4

    Science.gov (United States)

    Lavrentyev, A. A.; Gabrelian, B. V.; Vu, V. T.; Shkumat, P. N.; Parasyuk, O. V.; Fedorchuk, A. O.; Khyzhun, O. Y.

    2015-10-01

    We report on successful synthesis of high-quality single crystal of cesium mercury tetrabromide, Cs2HgBr4, by using the vertical Bridgman-Stockbarger method as well as on studies of its electronic structure. For the Cs2HgBr4 crystal, we have recorded X-ray photoelectron spectra for both pristine and Ar+ ion-bombarded surfaces. Our data indicate that the Cs2HgBr4 single crystal surface is rather sensitive with respect to Ar+ ion-bombardment. In particular, such a treatment of the Cs2HgBr4 single crystal surface alters its elemental stoichiometry. To explore peculiarities of the energy distribution of total and partial densities of states within the valence band and the conduction band of Cs2HgBr4, we have made band-structure calculations based on density functional theory (DFT) employing the augmented plane wave+local orbitals (APW+lo) method as incorporated in the WIEN2k package. The APW+lo calculations allow for concluding that the Br 4p states make the major contributions in the upper portion of the valence band, while its lower portion is dominated by contributors of the Hg 5d and Cs 5p states. Further, the main contributors to the bottom of the conduction band of Cs2HgBr4 are the unoccupied Br p and Hg s states. In addition, main optical characteristics of Cs2HgBr4 such as dispersion of the absorption coefficient, real and imaginary parts of dielectric function, electron energy-loss spectrum, refractive index, extinction coefficient and optical reflectivity have been explored from the first-principles band-structure calculations.

  16. Electron microscopy of primary cell cultures in solution and correlative optical microscopy using ASEM

    Energy Technology Data Exchange (ETDEWEB)

    Hirano, Kazumi; Kinoshita, Takaaki [Laboratory of Cell Biology, Department of Bioinformatics, Faculty of Engineering, Soka University, 1-236 Tangi-machi, Hachioji, Tokyo 192-8577 (Japan); Uemura, Takeshi [Department of Molecular Neurobiology and Pharmacology, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Department of Molecular and Cellular Physiology, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto, Nagano 390-8621 (Japan); Motohashi, Hozumi [Department of Gene Expression Regulation, Institute of Development, Aging and Cancer, Tohoku University, 4-1 Seiryo-cho, Aoba-ku, Sendai 980-8575 (Japan); Watanabe, Yohei; Ebihara, Tatsuhiko [Biomedical Research Institute, National Institute of Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8566 (Japan); Nishiyama, Hidetoshi [JEOL Ltd., 1-2 Musashino 3-chome, Akishima, Tokyo 196-8558 (Japan); Sato, Mari [Biomedical Research Institute, National Institute of Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8566 (Japan); Suga, Mitsuo [JEOL Ltd., 1-2 Musashino 3-chome, Akishima, Tokyo 196-8558 (Japan); Maruyama, Yuusuke; Tsuji, Noriko M. [Biomedical Research Institute, National Institute of Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8566 (Japan); Yamamoto, Masayuki [Department of Medical Biochemistry, Tohoku University Graduate School of Medicine, 2-1 Seiryo-cho, Aoba-ku, Sendai 980-8575 (Japan); Nishihara, Shoko, E-mail: shoko@soka.ac.jp [Laboratory of Cell Biology, Department of Bioinformatics, Faculty of Engineering, Soka University, 1-236 Tangi-machi, Hachioji, Tokyo 192-8577 (Japan); Sato, Chikara, E-mail: ti-sato@aist.go.jp [Biomedical Research Institute, National Institute of Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8566 (Japan)

    2014-08-01

    Correlative light-electron microscopy of cells in a natural environment of aqueous liquid facilitates high-throughput observation of protein complex formation. ASEM allows the inverted SEM to observe the wet sample from below, while an optical microscope observes it from above quasi-simultaneously. The disposable ASEM dish with a silicon nitride (SiN) film window can be coated variously to realize the primary-culture of substrate-sensitive cells in a few milliliters of culture medium in a stable incubator environment. Neuron differentiation, neural networking, proplatelet-formation and phagocytosis were captured by optical or fluorescence microscopy, and imaged at high resolution by gold-labeled immuno-ASEM with/without metal staining. Fas expression on the cell surface was visualized, correlated to the spatial distribution of F-actin. Axonal partitioning was studied using primary-culture neurons, and presynaptic induction by GluRδ2-N-terminus-linked fluorescent magnetic beads was correlated to the presynaptic-marker Bassoon. Further, megakaryocytes secreting proplatelets were captured, and P-selectins with adherence activity were localized to some of the granules present by immuno-ASEM. The phagocytosis of lactic acid bacteria by dendritic cells was also imaged. Based on these studies, ASEM correlative microscopy promises to allow the study of various mesoscopic-scale dynamics in the near future. - Highlights: • In situ correlative light electron microscopy of samples in open solution by ASEM. • Primary cultures for in-solution CLEM by developing SiN-film coating methods • First visualization of fluorescent magnetic beads in aqueous solution by CLEM. • Presynaptic induction of neurons by GluRδ2-N-terminus-coated beads studied by CLEM. • Axonal partitioning, bacterial phagocytosis, platelet formation imaged by CLEM.

  17. Synchronization trigger for HSFC in the optical diagnosis of intense electron beam cathodes

    International Nuclear Information System (INIS)

    Yang Jie; Shu Ting; Zhang Jun; Yang Jianhua; Liu Lie; Yin Yi; Luo Ling

    2010-01-01

    This paper presents an intense electron beam cathodes optical diagnosis platform, which consists of an accelerator using a water-dielectric helical pulse forming line (PFL) and a high speed framing camera (HSFC-PRO) with an minimum exposure of 3 ns. HSFC-PRO must work synchronously with the explosive process of the intense electron beam cathodes in order to obtain correct data. On one hand, the high voltage electrical pulse from the PFL is delayed by a water-dielectric helix line with a nearly 110ns electrical length. On the other hand, The synchronization trigger signal for the HSFC-PRO is obtained from the pre d elayed high voltage electrical pulse from the PFL. A TTL signal (5 V) with rising edge is required to trigger the HSFC. The rise time (10% to 90%) should be <20ns. As a result, the negative-edge attenuated electrical pulse with a about 25 ns rise time from the PFL can not trigger the HSFC immediately.Consequently, the polarity of the attenuated high voltage electrical pulse from the PFL is reversed by a pulse transformer. Then it is converted subsequently into a TTL signal (5 V) with rising edge via a monostable multivibrator , The rise time (10% to 90%) is <5 ns, which is suitable for HSFC absequently. This established optical diagnosis platform can supply an electrical pulse with its output voltage of 200-400 kV, risetime of ∼35ns and pulse width(FWHM) of ∼110ns. By means of delaying the electrical pulse, the synchronization trigger problem of the HSFC-PRO has been solved properly, with correlative time precision of about ns level, which sets a running start for the following intensive research of explosive emission cathodes. (authors)

  18. Mechanical, electronic, and optical properties of β-B{sub 6}O. First-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ruike; Ma, Shaowei; Wei, Qun [Xidian Univ., Shaanxi (China). School of Physics and Optoelectronic Engineering; Du, Zheng [National Supercomputing Center in Shenzhen, Shenzhen (China)

    2017-07-01

    The mechanical, electronic, and optical properties of β-B{sub 6}O are calculated by first-principles. The structural optimization and all properties are calculated by the method of generalized gradient approximation - Perdew, Burke and Ernzerhof (PBE). The hardness of β-B{sub 6}O is 39 GPa under a pressure of 0 GPa, which indicates that it belongs to a hard material. The band gap is indirect with a value of 1.836 eV, showing that β-B{sub 6}O is a semiconductor. The research of the electron localization function shows that the bonds of β-B{sub 6}O are covalent bonds, which can increase the stability of the compound. The phonon dispersion curves present the dynamical stability of β-B{sub 6}O under pressures of 0 and 50 GPa. The optical properties of β-B{sub 6}O are also calculated. In the energy range from 0 to 18 eV, β-B{sub 6}O presents high reflectivity; it has a strong absorption in the energy range from 3 to 18 eV. The refractive index results show that light propagates through the β-B{sub 6}O in a difficult manner in the energy range from 6.9 to 16.5 eV. In addition, the energy of the plasma frequency for β-B{sub 6}O is 16.6 eV and the peak value of the loss function is 13.6. These properties provide the basis for the development and application of β-B{sub 6}O.

  19. Electronic and optical properties of titanium nitride bulk and surfaces from first principles calculations

    Science.gov (United States)

    Mehmood, Faisal; Pachter, Ruth; Murphy, Neil R.; Johnson, Walter E.

    2015-11-01

    Prediction of the frequency-dependent dielectric function of thin films poses computational challenges, and at the same time experimental characterization by spectroscopic ellipsometry remains difficult to interpret because of changes in stoichiometry and surface morphology, temperature, thickness of the film, or substrate. In this work, we report calculations for titanium nitride (TiN), a promising material for plasmonic applications because of less loss and other practical advantages compared to noble metals. We investigated structural, electronic, and optical properties of stoichiometric bulk TiN, as well as of the TiN(100), TiN(110), and TiN(111) outermost surfaces. Density functional theory (DFT) and many-body GW methods (Green's (G) function-based approximation with screened Coulomb interaction (W)) were used, ranging from G0W0, GW0 to partially self-consistent sc-GW0, as well as the GW-BSE (Bethe-Salpeter equation) and time-dependent DFT (TDDFT) methods for prediction of the optical properties. Structural parameters and the band structure for bulk TiN were shown to be consistent with previous work. Calculated dielectric functions, plasma frequencies, reflectivity, and the electron energy loss spectrum demonstrated consistency with experiment at the GW0-BSE level. Deviations from experimental data are expected due to varying experimental conditions. Comparison of our results to spectroscopic ellipsometry data for realistic nanostructures has shown that although TDDFT may provide a computationally feasible level of theory in evaluation of the dielectric function, application is subject to validation with GW-BSE calculations.

  20. First-principles Study of the Electronic Structure and Optical Properties of MgH2

    Science.gov (United States)

    Alford, Ashley; Chou, Mei-Yin

    2003-03-01

    It has been noticed that magnesium might play an interesting role in recently discovered switchable-mirror systems. For example, the films of rare earth and magnesium alloys are found to be superior to the pure rare-earth samples in maximum transparency and mirror-state reflectivity [1]. Moreover, the magnesium-rich Ni-Mg alloy films turned out to be a switchable-mirror system without rare earths [2]. In both cases, pure transparent MgH2 is reversibly formed when these alloys take up hydrogen. In order to model the optical properties of these films, we need to know the electronic and optical properties of MgH2. In this work, we investigate its bonding characteristics, band structure, and dielectric properties with first-principles theoretical methods. The stability of the crystal and the bonding are studied using density functional theory and pseudopotential methods. The excited state properties (the quasiparticle spectra) are studied by many-body perturbation theory within the so-called GW approximation in which the electronic self-energy is approximated by the full Green's function (G) times the screened Coulomb interaction (W). We will report the results for both the rutile-structured alpha-MgH2 and the low-symmetry gamma-MgH2. [1] P. van der Sluis, M. Ouwerkerk, and P. A. Duine, Appl. Phys. Lett. 70, 3356 (1997). [2] T. J. Richardson, J. L. Slack, R. D. armitage, R. Kostecki, B. Farangis, and M. D. Rubin, Appl. Phys. Lett. 78, 3047 (2001).

  1. Electronic and optical properties of titanium nitride bulk and surfaces from first principles calculations

    International Nuclear Information System (INIS)

    Mehmood, Faisal; Pachter, Ruth; Murphy, Neil R.; Johnson, Walter E.

    2015-01-01

    Prediction of the frequency-dependent dielectric function of thin films poses computational challenges, and at the same time experimental characterization by spectroscopic ellipsometry remains difficult to interpret because of changes in stoichiometry and surface morphology, temperature, thickness of the film, or substrate. In this work, we report calculations for titanium nitride (TiN), a promising material for plasmonic applications because of less loss and other practical advantages compared to noble metals. We investigated structural, electronic, and optical properties of stoichiometric bulk TiN, as well as of the TiN(100), TiN(110), and TiN(111) outermost surfaces. Density functional theory (DFT) and many-body GW methods (Green's (G) function-based approximation with screened Coulomb interaction (W)) were used, ranging from G 0 W 0 , GW 0 to partially self-consistent sc-GW 0 , as well as the GW-BSE (Bethe-Salpeter equation) and time-dependent DFT (TDDFT) methods for prediction of the optical properties. Structural parameters and the band structure for bulk TiN were shown to be consistent with previous work. Calculated dielectric functions, plasma frequencies, reflectivity, and the electron energy loss spectrum demonstrated consistency with experiment at the GW 0 -BSE level. Deviations from experimental data are expected due to varying experimental conditions. Comparison of our results to spectroscopic ellipsometry data for realistic nanostructures has shown that although TDDFT may provide a computationally feasible level of theory in evaluation of the dielectric function, application is subject to validation with GW-BSE calculations

  2. Microstructure, electronic structure and optical properties of combustion synthesized Co doped ZnO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Srinatha, N. [Department of Physics, JB Campus, Bangalore University, Bangalore 560056 (India); Nair, K.G.M. [UGC-DAE-CSR, Kalpakkam Node, Kalpakkam, Kokilamedu 603102 (India); Angadi, Basavaraj, E-mail: brangadi@gmail.com [Department of Physics, JB Campus, Bangalore University, Bangalore 560056 (India)

    2015-10-01

    We report on the microstructure, electronic structure and optical properties of nanocrystalline Zn{sub 1−x}Co{sub x}O (x=0, 0.01, 0.03, 0.05 and 0.07) particles prepared by solution combustion technique using L-Valine as fuel. The detailed structural and micro-structural studies were carried out by XRD, HRTEM and TEM-SAED respectively, which confirms the formation of single phased, nano-sized particles. The electronic structure was determined through NEXAFS and atomic multiplet calculations/simulations performed for various symmetries and valence states of ‘Co’ to determine the valance state, symmetry and crystal field splitting. The correlations between the experimental NEXAFS spectra and atomic multiplet simulations, confirms that, ‘Co’ present is in the 2+ valence state and substituted at the ‘Zn’ site in tetrahedral symmetry with crystal field splitting, 10Dq =−0.6 eV. The optical properties and ‘Co’ induced defect formation of as-synthesized materials were examined by using diffuse reflectance and Photoluminescence spectroscopy, respectively. Red-shift of band gap energy (E{sub g}) was observed in Zn{sub 1−x}Co{sub x}O samples due to Co (0.58 Å) substitution at Zn (0.60 Å) site of the host ZnO. Also, in PL spectra, a prominent pre-edge peak corresponds to ultraviolet (UV) emission around 360–370 nm was observed with Co concentration along with near band edge emission (NBE) of the wide band gap ZnO and all samples show emission in the blue region.

  3. Improving the visualization of electron-microscopy data through optical flow interpolation

    KAUST Repository

    Carata, Lucian

    2013-01-01

    Technical developments in neurobiology have reached a point where the acquisition of high resolution images representing individual neurons and synapses becomes possible. For this, the brain tissue samples are sliced using a diamond knife and imaged with electron-microscopy (EM). However, the technique achieves a low resolution in the cutting direction, due to limitations of the mechanical process, making a direct visualization of a dataset difficult. We aim to increase the depth resolution of the volume by adding new image slices interpolated from the existing ones, without requiring modifications to the EM image-capturing method. As classical interpolation methods do not provide satisfactory results on this type of data, the current paper proposes a re-framing of the problem in terms of motion volumes, considering the depth axis as a temporal axis. An optical flow method is adapted to estimate the motion vectors of pixels in the EM images, and this information is used to compute and insert multiple new images at certain depths in the volume. We evaluate the visualization results in comparison with interpolation methods currently used on EM data, transforming the highly anisotropic original dataset into a dataset with a larger depth resolution. The interpolation based on optical flow better reveals neurite structures with realistic undistorted shapes, and helps to easier map neuronal connections. © 2011 ACM.

  4. First principles study of structural, electronic and optical properties of KCl crystal

    International Nuclear Information System (INIS)

    Chen, Z.J.; Xiao, H.Y.; Zu, X.T.

    2006-01-01

    The structural, electronic and optical properties of KCl crystal in B1, B2, B3 and T1 structures have been systematically studied using first-principle pseudopotential calculations. In addition, pressure-induced phase transition has also been investigated. It was found that when the pressure is below 2.8 GPa, the B1 structure is the most stable. Above 2.8 GPa KCl crystal will undergo a structural phase transition from the relatively open NaCl structure into the more dense CsCl atomic arrangement. Our results also suggested that at about 1.2 GPa structural phase transition from B3 to T1 will occur. When the pressure arrives at 39.9 GPa, the phase transition will occur from B2 to T1. In addition, we found KCl Crystal has indirect band gap in B2 structure and direct band gap in B1, B3 and T1 structures. The band gap value is the smallest in the T1 structure and is the largest in the B1 and B3 structures. Our calculations are found to be in good agreement with available experimental and theoretical results. The dielectric function and energy loss function of KCl crystal in four structures (B1, B2, B3 and T1) have been calculated as well as the anisotropy of the optical properties of KCl crystal in T1 structure

  5. Analysis of optical and electronic properties of MoS2 for optoelectronics and FET applications

    Science.gov (United States)

    Ullah, Muhammad S.; Yousuf, Abdul Hamid Bin; Es-Sakhi, Azzedin D.; Chowdhury, Masud H.

    2018-04-01

    Molybdenum disulfide (MoS2) is considered as a promising alternative to conventional semiconductor materials that used in the IC industry because of its novel properties. In this paper, we explore the optical and electronic properties of MoS2 for photodetector and transistors applications. This simulation is done using `DFT materials properties simulator'. Our findings show that mono- and multi-layer MoS2 is suitable for conventional and tunnel FET applications due to direct and indirect band-gap respectively. The bulk MoS2 crystal, which are composed of stacked layers have indirect bandgap and mono-layer MoS2 crystal form direct bandgap at the K-point of Brillouin zone. Indirect bandgap of bulk MoS2 crystal implies that phonons need to be involved in band-to-band tunneling (BTBT) process. Degenerately doped semiconductor, which is basically spinning the Fermi level, changing the DOS profile, and thinning the indirect bandgap that allow tunneling from valence band to conduction band. The optical properties of MoS2 is explored in terms of Absorption coefficient, extinction coefficient and refractive index. Our results shows that a MoS2 based photodetector can be fabricate to detect light in the visible range (below 500nm). It is also observed that the MoS2 is most sensitive for the light of wavelength 450nm.

  6. Electronic, elastic, and optical properties of monolayer BC{sub 2}N

    Energy Technology Data Exchange (ETDEWEB)

    Jiao, Lina; Hu, Meng; Peng, Yusi; Luo, Yanting; Li, Chunmei; Chen, Zhiqian, E-mail: chen_zq@swu.edu.cn

    2016-12-15

    The structural stability, electronic structure, elasticity, and optical properties of four types of monolayer BC{sub 2}N have been investigated from first principles using calculation based on density functional theory. The results show that the structural stability of BC{sub 2}N increases with the number of C–C and B–N bonds. By calculating the two-dimensional Young's modulus, shear modulus, Poisson's ratio, and shear anisotropic factors in different directions, four structures present various anisotropies and the most stable structure is almost isotropic. For C-type BC{sub 2}N, the values of two-dimensional Young's modulus, shear modulus, and bulk modulus (309, 128, 195 GPa m{sup −1}), are smaller than those of graphene (343, 151, 208) but bigger than those of h-BN (286, 185, 116). Furthermore, the dielectric function, refractive index, reflectivity, absorption coefficient, and energy loss spectrum are also calculated to investigate the mechanism underpinning the optical transitions in BC{sub 2}N, revealing monolayer BC{sub 2}N as a candidate window material. - Graphical abstract: Schematic diagram of BC{sub 2}N under the biaxial tensile strain. Changes in the valence-band top and the conduction-band bottom of BC{sub 2}N with increasing strain.

  7. Optical and Electrical Properties of Tin-Doped Cadmium Oxide Films Prepared by Electron Beam Technique

    Science.gov (United States)

    Ali, H. M.; Mohamed, H. A.; Wakkad, M. M.; Hasaneen, M. F.

    2009-04-01

    Tin-doped cadmium oxide films were deposited by electron beam evaporation technique. The structural, optical and electrical properties of the films were characterized. The X-ray diffraction (XRD) study reveals that the films are polycrystalline in nature. As composition and structure change due to the dopant ratio and annealing temperature, the carrier concentration was varied around 1020 cm-3, and the mobility increased from less than 10 to 45 cm2 V-1 s-1. A transmittance value of ˜83% and a resistivity value of 4.4 ×10-4 Ω cm were achieved for (CdO)0.88(SnO2)0.12 film annealed at 350 °C for 15 min., whereas the maximum value of transmittance ˜93% and a resistivity value of 2.4 ×10-3 Ω cm were obtained at 350 °C for 30 min. The films exhibited direct band-to-band transitions, which corresponded to optical band gaps of 3.1-3.3 eV.

  8. Optical Analysis of Iron-Doped Lead Sulfide Thin Films for Opto-Electronic Applications

    Science.gov (United States)

    Chidambara Kumar, K. N.; Khadeer Pasha, S. K.; Deshmukh, Kalim; Chidambaram, K.; Shakil Muhammad, G.

    Iron-doped lead sulfide thin films were deposited on glass substrates using successive ionic layer adsorption and reaction method (SILAR) at room temperature. The X-ray diffraction pattern of the film shows a well formed crystalline thin film with face-centered cubic structure along the preferential orientation (1 1 1). The lattice constant is determined using Nelson Riley plots. Using X-ray broadening, the crystallite size is determined by Scherrer formula. Morphology of the thin film was studied using a scanning electron microscope. The optical properties of the film were investigated using a UV-vis spectrophotometer. We observed an increase in the optical band gap from 2.45 to 3.03eV after doping iron in the lead sulfide thin film. The cutoff wavelength lies in the visible region, and hence the grown thin films can be used for optoelectronic and sensor applications. The results from the photoluminescence study show the emission at 500-720nm. The vibrating sample magnetometer measurements confirmed that the lead sulfide thin film becomes weakly ferromagnetic material after doping with iron.

  9. Medical Application of Free Electron Laser Trasmittance using Hollow Optical Fiber

    CERN Document Server

    Suzuki, Sachiko; Ishii, Katsonuri

    2004-01-01

    Mid-infrared Free Electron Laser (FEL) is expected as new application for biomedical surgery. However, delivery of MIR-FEL into the body is difficult because the common glass optical fibers have strong absorption at MIR region. A good operational and flexible line for FEL is required at medical field. A Hollow optical fiber is developed for IR laser and high-power laser delivery. We evaluated the fiber for FEL transmission line. This fiber is coated with cyclic olefin polymer (COP) and silver thin film on the inside of glass capillary tube. It is 700 μm-bore and 1m in lengths. The fiber transmission loss of the measured wavelength region of 5.5 μm to 12 μm is less than 1dB/m when the fiber is straight and 1.2 dB/m when bent to radius of 20 cm. Additionally, the output beam profile and the pulse structure is not so different form incidence beam. In conclusion, the fiber is suitable for delivery of the FEL energy for applications in medical and laser surgery.

  10. Electron paramagnetic resonance and optical properties of Cr3+ doped YAl3(BO3)4

    International Nuclear Information System (INIS)

    Wells, Jon-Paul R; Yamaga, Mitsuo; Han, Thomas P J; Honda, Makoto

    2003-01-01

    We report on the electron paramagnetic resonance (EPR) and optical absorption and fluorescence spectroscopy of YAl 3 (BO 3 ) 4 single crystals doped with 0.2 mol% of trivalent chromium. From EPR we determine that the Cr 3+ ions reside in sites of essentially octahedral symmetry with an orthorhombic distortion. The ground state 4 A 2 splitting is determined to be 2√D 2 + 3E 2 ∼ 1.05 ± 0.04 cm -1 , where D and E are fine-structure parameters, and we can attribute this splitting to the combined effect of a low-symmetry distortion and spin-orbit coupling. The g-values and fine-structure parameters D and E of the ground state 4 A 2 are measured to be g x ∼ g y ∼ g z = 1.978 ± 0.005, vertical bar D vertical bar = 0.52 ± 0.02 cm -1 and vertical bar E vertical bar 0.010 ± 0.005 cm -1 respectively. From 10 K optical absorption we have measured the position and crystal-field splittings of the 2 E, 2 T 1 , 4 T 2 , 2 T 2 and 4 T 1 states with the 4 T 2 and 4 T 1 levels appearing as vibronically broadened bands

  11. Optical and electron transport properties of reactively sputtered Cu/sub x/S

    International Nuclear Information System (INIS)

    Leong, J.Y.C.

    1980-01-01

    Thin films of Cu/sub x/S were deposited on glass slides by sputtering Cu in a reactive H 2 S/Ar environment. Optical transmittance and reflectance measurements were used to explore the infrared absorption spectra of the material. Analysis of the absorption edge characteristics resulted in the identification of an indirect bandgap at 1.15 (+-.05) eV, a direct bandgap at 1.30 (+-.05) eV, and an electron effective mass of 1.0 (+-0.2) m 0 . Electrical data consisting of resistivity and Hall effect measurements from liquid nitrogen to room temperature were analyzed to determine the dominant scattering mechanisms limiting the hole mobility in the material. Ionized impurity scattering was the dominant mechanism at low temperatures (T 0 K) and polar optical phonon scattering was most effective at high temperatures (T > 150 0 K). All films were p-type. Effects of sputtering gas pressure, heat treatments, and temperature on the properties were studied

  12. Influence of chromium concentration on the optical-electronic properties of ruby microstructures

    International Nuclear Information System (INIS)

    Cossolino, L C; Zanatta, A R

    2010-01-01

    Films of amorphous aluminium nitride (AlN) were prepared by conventional radio frequency sputtering of an Al + Cr target in a plasma of pure nitrogen. The Cr-to-Al relative area determines the Cr content, which remained in the ∼0-3.5 at% concentration range in this study. Film deposition was followed by thermal annealing of the samples up to 1050 0 C in an atmosphere of oxygen and by spectroscopic characterization through energy dispersive x-ray spectrometry, photoluminescence and optical transmission measurements. According to the experimental results, the optical-electronic properties of the Cr-containing AlN films are highly influenced by both the Cr concentration and the temperature of the thermal treatments. In fact, thermal annealing at 1050 0 C induces the development of structures that, because of their typical size and distinctive spectral characteristics, were designated by ruby microstructures (RbMSs). These RbMSs are surrounded by a N-rich environment in which Cr 3+ ions exhibit luminescent features not present in other Cr 3+ -containing systems such as ruby, emerald or alexandrite. The light emissions shown by the RbMSs and surroundings were investigated according to the Cr concentration and temperature of measurement, allowing the identification of several Cr 3+ -related luminescent lines. The main characteristics of these luminescent lines and corresponding excitation-recombination processes are presented and discussed in view of a detailed spectroscopic analysis.

  13. 3rd International Conference on Opto-Electronics and Applied Optics

    CERN Document Server

    Chakrabarti, Satyajit; Reehal, Haricharan; Lakshminarayanan, Vasudevan

    2017-01-01

    The Proceedings of 3rd International Conference on Opto-Electronics and Applied Optics, OPTRONIX 2016 is an effort to promote and present the research works by scientists and researchers including students in India and abroad in the area of Green Photonics and other related areas as well as to raise awareness about the recent trends of research and development in the area of the related fields. The book has been organized in such a way that it will be easier for the readers to go through and find out the topic of their interests. The first part includes the Keynote addresses by Rajesh Gupta, Department of Energy Science and Engineering, Indian Institute of Technology, Bombay; P.T. Ajith Kumar, President and Leading Scientist Light Logics Holography and Optics, Crescent Hill, Trivandrum, Kerala; and K.K. Ghosh, Institute of Engineering & Management, Kolkata, India.  The second part focuses on the Plenary and Invited Talks given by eminent scientists namely, Vasudevan Lakshminarayanan, University of Wate...

  14. Electronic, elastic and optical properties of ZnGeP{sub 2} semiconductor under hydrostatic pressures

    Energy Technology Data Exchange (ETDEWEB)

    Tripathy, S.K.; Kumar, V., E-mail: vkumar52@hotmail.com

    2014-03-15

    The electronic, elastic and optical properties of zinc germanium phosphide, ZnGeP{sub 2}, semiconductor have been studied using local density approximation (LDA) method within the density functional theory (DFT). The lattice constants (a and c), band structure, density of states (DOS), bulk modulus (B) and pressure derivative of bulk modulus (B′) have been discussed. The value of pseudo-direct band gap (E{sub g}) at Γ point has been calculated. The pressure dependences of elastic stiffness coefficients (C{sub ij}), Zener anisotropy factor (A), Poisson's ratio (ν), Young modulus (Y) and shear modulus (G) have also been calculated. The ratio of B/G shows that that ZnGeP{sub 2} is ductile in nature. The optical properties have been discussed in detail under three different pressures in the energy range 0–22 eV. The calculated values of all parameters are compared with the available experimental values and the values reported by different workers. Reasonably good agreement has been obtained between them.

  15. Optical absorption and electron spin resonance in natural, irradiated and heated spodumene

    International Nuclear Information System (INIS)

    Ito, A.S.; Isotani, S.

    1983-09-01

    Heat treatment and X and γ-Rays irradiation of lylac and colorless natural spodumene, LiAlSi 2 O 6 , have been studied. Irradiation produces a color change, from lylac or colorless to green. Irradiated samples heated at 200 0 C turn lylac and bleach at 400 0 C. Optical absorption spectra were decomposed into gaussian line shape bands and it is observed that green and lylac centers are simultaneously created by irradiation. These centers are independent from each other. Optical absorption, EPR and X-Ray fluorescence results show the spectra of impurities, responsible by the presence of the created centers and indicated Mn participation in the process of centers creation and destruction. Decay Kinetics of green and lylac centers have been studied and it is observed that simple Kinetic models do not apply to these cases. An empirical fit allowed the calculation of activation energies of the lylac and green centers decays. Discussions about the present results led us to propose a new model where the green and lylac centers are due to Mn 3+ ions in two different Al 3+ sites, whose absorption are intensified by the interaction with an electron trapped in a neighbour oxygen. (Author) [pt

  16. Measurement of electron density and electron temperature of a cascaded arc plasma using laser Thomson scattering compared to an optical emission spectroscopic approach

    Science.gov (United States)

    Yong, WANG; Cong, LI; Jielin, SHI; Xingwei, WU; Hongbin, DING

    2017-11-01

    As advanced linear plasma sources, cascaded arc plasma devices have been used to generate steady plasma with high electron density, high particle flux and low electron temperature. To measure electron density and electron temperature of the plasma device accurately, a laser Thomson scattering (LTS) system, which is generally recognized as the most precise plasma diagnostic method, has been established in our lab in Dalian University of Technology. The electron density has been measured successfully in the region of 4.5 × 1019 m-3 to 7.1 × 1020 m-3 and electron temperature in the region of 0.18 eV to 0.58 eV. For comparison, an optical emission spectroscopy (OES) system was established as well. The results showed that the electron excitation temperature (configuration temperature) measured by OES is significantly higher than the electron temperature (kinetic electron temperature) measured by LTS by up to 40% in the given discharge conditions. The results indicate that the cascaded arc plasma is recombining plasma and it is not in local thermodynamic equilibrium (LTE). This leads to significant error using OES when characterizing the electron temperature in a non-LTE plasma.

  17. Quantum theory of the electronic and optical properties of low-dimensional semiconductor systems

    Science.gov (United States)

    Lau, Wayne Heung

    This thesis examines the electronic and optical properties of low-dimensional semiconductor systems. A theory is developed to study the electron-hole generation-recombination process of type-II semimetallic semiconductor heterojunctions based on a 3 x 3 k·p matrix Hamiltonian (three-band model) and an 8 x 8 k·p matrix Hamiltonian (eight-band model). A novel electron-hole generation and recombination process, which is called activationless generation-recombination process, is predicted. It is demonstrated that the current through the type-II semimetallic semiconductor heterojunctions is governed by the activationless electron-hole generation-recombination process at the heterointerfaces, and that the current-voltage characteristics are essentially linear. A qualitative agreement between theory and experiments is observed. The numerical results of the eight-band model are compared with those of the threeband model. Based on a lattice gas model, a theory is developed to study the influence of a random potential on the ionization equilibrium conditions for bound electron-hole pairs (excitons) in III--V semiconductor heterostructures. It is demonstrated that ionization equilibrium conditions for bound electron-hole pairs change drastically in the presence of strong disorder. It is predicted that strong disorder promotes dissociation of excitons in III--V semiconductor heterostructures. A theory of polariton (photon dressed by phonon) spontaneous emission in a III--V semiconductor doped with semiconductor quantum dots (QDs) or quantum wells (QWs) is developed. For the first time, superradiant and subradiant polariton spontaneous emission phenomena in a polariton-QD (QW) coupled system are predicted when the resonance energies of the two identical QDs (QWs) lie outside the polaritonic energy gap. It is also predicted that when the resonance energies of the two identical QDs (QWs) lie inside the polaritonic energy gap, spontaneous emission of polariton in the polariton

  18. Applications of electron lenses: scraping of high-power beams, beam-beam compensation, and nonlinear optics

    Energy Technology Data Exchange (ETDEWEB)

    Stancari, Giulio

    2014-09-11

    Electron lenses are pulsed, magnetically confined electron beams whose current-density profile is shaped to obtain the desired effect on the circulating beam. Electron lenses were used in the Fermilab Tevatron collider for bunch-by-bunch compensation of long-range beam-beam tune shifts, for removal of uncaptured particles in the abort gap, for preliminary experiments on head-on beam-beam compensation, and for the demonstration of halo scraping with hollow electron beams. Electron lenses for beam-beam compensation are being commissioned in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL). Hollow electron beam collimation and halo control were studied as an option to complement the collimation system for the upgrades of the Large Hadron Collider (LHC) at CERN; a conceptual design was recently completed. Because of their electric charge and the absence of materials close to the proton beam, electron lenses may also provide an alternative to wires for long-range beam-beam compensation in LHC luminosity upgrade scenarios with small crossing angles. At Fermilab, we are planning to install an electron lens in the Integrable Optics Test Accelerator (IOTA, a 40-m ring for 150-MeV electrons) as one of the proof-of-principle implementations of nonlinear integrable optics to achieve large tune spreads and more stable beams without loss of dynamic aperture.

  19. Electronic and optical properties of ZrB{sub 12} and YB{sub 6}. Discussion on electron-phonon coupling

    Energy Technology Data Exchange (ETDEWEB)

    Teyssier, J.; Kuzmenko, A.; Marel, D. van der; Lortz, R.; Junod, A. [Departement de Physique de la Matiere Condensee, Universite de Geneve, Quai Ernest-Ansermet 24, 1211 Geneve 4 (Switzerland); Filippov, V.; Shitsevalova, N. [Institute for Problems of Materials Science NANU, Kiev (Ukraine)

    2006-09-15

    We report the optical properties of high-quality single crystals of low temperature superconductors zirconiumdodecaboride ZrB{sub 12} (T{sub c}=5.95 K) and yttrium hexaboride YB{sub 6} (T{sub c}=7.15 K) in the range 6 meV-4.6 eV at room temperature. The experimental optical conductivity was extracted from the analysis of the reflectivity in the infrared range and ellipsometry measurement of the dielectric function in the visible range. The electronic band structure of these compounds was calculated by the self-consistent full-potential LMTO method and used to compute the interband part of the optical conductivity and the plasma frequency {omega}{sub p}. A good agreement was observed between the interband part of the experimental optical conductivities and the band structure calculations. Different methods combining optical spectroscopy, resistivity, specific heat measurements and results of band structure calculations are used to determine the electron-phonon coupling constant. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Donor–Acceptor Copolymers of Relevance for Organic Photovoltaics: A Theoretical Investigation of the Impact of Chemical Structure Modifications on the Electronic and Optical Properties

    KAUST Repository

    Pandey, Laxman; Risko, Chad; Norton, Joseph E.; Bré das, Jean-Luc

    2012-01-01

    We systematically investigate at the density functional theory level how changes to the chemical structure of donor-acceptor copolymers used in a number of organic electronics applications influences the intrinsic geometric, electronic, and optical